Unlike the former MSN -- we do not have the luxury of having photo albums attached to the Proboard site.
You will need to find your own album (paid or free) so you can share images or share a link to your album. (also acceptable in your signature).
Free albums can be found at LiveJournal, Wordpress, Flickr. Dropbox offers files. Each of the free ones offer x amount of space.
Photobucket, Fotki, and PictureTrail are now paid sites and unless you pay, then you can share.
If you have a Google account, you can use albums there BUT you can not share the photos on the board, just a link to the photo or album.
Proboards does allow uploads but there is a limit on a free account.