Yeah, posting the thumbnail that the gallery makes should be fine. Posting anything larger than 700px wide should be frowned upon.
Yes Bob - upload your photos to the gallery, then as Ben says you can copy the vB code in the box below (where it says "linked thumbnail") and paste it into your post, which will give you a small clickable photo like this:
Well, I prefer the "medium sized image" over "linked thumbnail" but whatever.