Assuming you're using the official Facebook app, yes. Just click on "photo" up top and then you can either take one or choose from your Library. I'm not familiar with the other FB apps, but I assume they have similar features.
Why you can't do this from the Library/Gallery I do not know. The gallery is really missing a ton of sharing options. Not to harp on "the other OS" but my gallery on my Android phone blows the iPad's away since I can send/share the photo with pretty much any app I have installed that supports photos of any kind (for example, I see Google Goggles, Print, Bluetooth, Picasa, Handcent (SMS), PicSay (my photo editing app of choice), Twitter, Google+, Evernote, Catch, Facebook, Email, Skype and several others).
On my iPad my "sharing" options are to email it or Tweet it. Wow...I just can't decide given so many options! Perhaps there's a better gallery app available for iPad that offers some more sharing functionality? Anyone know?
