To actually answer your question instead of pulling out the 'legal ramifications' card...
There is at least one site online that's done a review of the core books, including the MM. The review has nearly every MM picture in some form or another included, albeit with the proper trademark and copyright information imbedded in the pic.
Wizards.com has quite a few black and white images of various creatures... you might get lucky and find the one you're looking for.
Google's image search is very helpful for looking for the obscure ones... like 'glatezabu" or something like that.
Check around the web in general for monster pics... they may not be from the MM, but they'll help give your players an idea of what the thing looks like.
Hotline has an excellent DnD community... images of monsters are quite easy to come by there. Just don't download pirated copies of copyrighted books!
Usenet probably has some good stuff too, if you know where to look.
Conversely, you could just buy a scanner and a nice printer
-F