Originally Posted by funbun
What size do the thumbnails have to be?
The forum software makes the thumbnails. You just attach your file and let the program do the rest. Then the forum reader just clicks on the thumbnail to get the full-sized image.
There is probably a limit (100k?) to the overall size of the file you attach. And try to make it a pixel count that'll easily fit on the screen. Say 800x600 or less.