Work on vb4.1.5pl1.
Thank you for this mod!!

Note:
Update instruction for v4.1.5pl1
to

anyway this can be used on the cms front page? i'd like to show my latest threads and have the thread thumbnail show up with it, is that possible?

I do not use the CMS function :(
I will take a look a it from my test site , for curiosity ;)

Currently, when "first image in post" (source2) is set, it won't display thumbnails from attachments. When "first attachment" (source1) is set, it won't display thumbnails from the first image. But often, you would like to have a combination of these options, instead of excluding each other.

You can solve this by doing this:
1) set the thumbnail source to "First Attachment".
2) go to plugin manager > "Forum Display - Threadbit Display" > find the line containing
$hook_query_fields .= ", MIN(attachment.attachmentid) AS attachmentid";
and append under that line, the following line:
$hook_query_fields .= ", thread.thumbnailurl AS thumbnailurl";

That's all.

I'm not sure this would work my friend!
Let me check it out

The "No Thumb" Image Doesnt Appear For Me... :( What Should i Do?

Did you have you added the scripts from the instruction in every templates??
If thumbs are not showing, normally it's because you are missing the threadbit script.
Or you didn't add the forums from the options?!?!

Is it work with the align codecs?
center, left, right??
because are someone who not work with them....

excuse me my english :S

I would love this mod to be able to do this :)

Does this mod work with the forums' search function?