There seems to only be 2 options that is fullsize or thumbnail. Shouldnt there be an option to post medium sized images or collages in the forums? the fullsize images look goofy and the thumbnails are too small to see.
You can also change "Attachment Thumbnail Dimensions" under Attachment Options. I don't remember what the (too small) default was, but I increased it to 250px, which seems about right. Big enough to show reasonable detail, but not overpowering like full size images. Most users can see 3 or 4 thumbnails in a row on "normal" sized screens. And we used one of AndyB's add-ons to disable inserting full size images in posts - except for admins/mods. Oversize images in posts were driving us crazy.