When you write a post, right above the subject line is a row of icons. More or less in the middle are two "camera" icons. The one on the left with the upload arrow is for new images you want to upload to BGG from your computer. The right hand one is for images you already have in your personal gallery.
The little "tree" icon to their right is for uploading images from the web.
Well how about that? I need to work on my observational skills. That is cool. Thanks for the info.