Adding an image to you HTML signature in Thunderbird requires a slight HTML hackery. You need to locate the image on disk and add the IMG tag with the src attribute using the file URL of the image:
Linux:
<IMG src="file:///home/brian/.mozilla-thunderbird/image.jpg" alt="Cool"/>
Windows:
<IMG src="file://c:/foobar/image.jpg" alt="Cool"/>
Invert your Mind 
Thank you very much!
I was trying for days to solve my “blank” image problem.
Really thank you.
LikeLike
Any chance that anyone has the the appropriate code for adding an image in mac os 10.4??
LikeLike
Thank you! Thank you! Thank you! I don’t know how many times I’ve asked advice on how to get my images to show. You’re a legend!
LikeLike
This can’t work. When the recipient gets the e-mail, his or her e-mail client will look on his local hard drive (because you’re referencing a local image, and it’s local to whomever) and not find it, displaying a blank image.
If you post the image to the web, and then reference it like http://www.example.com/hello.jpg, then it should work fine.
LikeLike
@Tom – It works because Thunderbird realizes that you are referencing a local image and includes it in the multipart MIME body of the email. It’s just a cool trick with Thunderbird and might not work with other email clients.
Your solution will work as well, but in general you shouldn’t reference images external to the email itself. You really should attach all the images as part of the email message that you are using inside the HTML of the email message. This is the correct way to send HTML emails and will work with all email clients and also will prevent some clients from not rendering the images without the user clicking a button.
LikeLike
I can’t get this to work. Signature looks perfect with embedded image, but Thunderbird won’t send it. It just keeps trying to attach the image for ever and never sends the email.
I must have visited every forum & helpsite on the web by now, and all give more or less the same html lines for the signature file, so I really, really don’t understand why it’s not working.
(neither with Ubuntu nor with Windows, both TB 2.0)
LikeLike
I can confirm Milly’s finding. If it works at all, at best it does not work very reliably on Thunderbird 2.x
LikeLike
I’m having the same problem as Milly. IF I can get the image to work, Thunderbird just sits there and won’t send.
LikeLike
Try putting the image on the root folder. I could only get it to work by using file://c:/image.jpg
LikeLike
I had the problem too. Here is what worked for me: http://email.about.com/od/mozillathunderbirdtips/qt/et_tb_sig_image.htm
Worked like a charm
LikeLike
Ernst has it right. All the other tries just proved to be exercises in frustration.
This works, and as near as I can tell, the images stay intact when mail is sent, forwarded, etc.
Way to go Ernst!
LikeLike
I had the same problem as Ernst. When I looked at the html file thunderbird created after I followed the instructions, I saw that the source directory path had been changed to include %20 in place of the spaces. I believe this is the problem that many of you are facing. If you prefer to use the html in the account settings window I believe this should resolve the problem. For example:
file://C:/My Pictures/My Logo File.jpg
changes to
file://C:/My%20Pictures/My%20Logo%20File.jpg
Those of you that use a language that uses accents and non-english characters in the path and filename might have other problems.
LikeLike
The best way to attach the image into your signature without using any of the path for local disk nor online is to insert the encoded image in the signature:
This way you avoid the problem of moving, deleting or renaming the image and also your recipients has no inconvenience with confirming the remote content in case the image is online…
LikeLike
TB 11 suddenly quit including my logo in my signature. I used both options: Insert signature as html and insert as file. Neither of them worked. I tried add ons, they did not help, either. As the add ons failed, I understood this was down to to TB and not the signature -also as it was displaying correctly in the beginning-.
After trying som more things, lastly I changed the file extension from .png to .gif and made the same change in the signature html code in TB. It worked!!! After that I renamed the files with correct extension and made the same changes in the signature file. It now works as it used to.
The code I use -obviously without the “”:
“My Name”
“Profession”
“”
“”
“Address Line 1”
“Address Line 2”
“Phone”
“E-mail: my.name@company.com”
Hope it helps…
LikeLike
Sorry, the web site used the html codes I quoted…
LikeLike
Hey Man you rock thanks for the tip.
Justo one more question, how do i make thunderbird respond and forword in the top op the mail string brecause wen i respond the message is gos to the botton of the string mail.
Thanks.
LikeLike
Bryan, I’m not sure how to do that, but I’m assuming there is a configuration option like “Start reply above quoted text”. I haven’t used Thunderbird in a while, so I don’t know what it looks like or can do now.
LikeLike
Thanks a lot folk!
LikeLike
i am facing the problem with signature that i can’t do any formatting in signature textbox & also i am unable to use my company logo in my signature,
I want answer regarding this but not in HTML or HTML format .
LikeLike
Easiest, IMHO, is to use Thunderbird’s compose window to create your signature, using the formatting tools and Insert options to manage the html for you. There is an option under Insert|Image to “Attach this image to the message” so you can choose to embed your pictures, or not.
File|Save as|HTML, then select the resultant file as your signature.
Or am I missing the point? Do the clientèle here prefer to do it the hard way? 😉
LikeLike
i dont understand the instructions at the top that everyone says thank you for. in english please for someone who does not have IT knowledge
LikeLike
@nate – In order to use this method, it will require a bit of knowledge about file systems and HTML. If you can follow the img tag bits above, then all you need to do is locate your image on the file system. You can also try @Chris suggestion about using the Thunderbird compose window.
LikeLike
Hello,
I have been able to add images to my signature but on the receivers side the images shows as i want it but also as an attachment? how could i remove that attachment?
Here is a link of what im talking about https://www.westtexasatv.com/wp-content/uploads/2013/07/image_02.png
thank you
LikeLike
This is because Thunderbird is attaching the image in the signature as an attachment (MIME attachment). There isn’t much you can do to fix this unless you use a publicly accessible URL instead of a local file URL for your image. You might try using Flickr or a similar type of image service to get it working. The HTML would look like:
<img src=”http://flickr.com/some-image/path/stuff/here”/>
LikeLike
I successfully created the HTML signature but although the signature is attached for every message, the image link is broken. Even though when I double-click the image to open the dialog box and “Attach the image” is selected, the image won’t appear until I click OK in that dialog box. The extra step is really annoying – any tips?
LikeLike
WOW. Seriously now, I’ve been looking at a way to solve my missing pictures in TB html signatures and everyone’s posts just did not make sense. Tried them all, and all showed missing pictures. I land here, try your recommendations, and BAM! It finally works. After a few months of trying. Thank you Brian for this awesome, detailed, and ACCURATE post!
God bless you man!
LikeLike