Hi LT
Why not create the thumbnail (any size you want) and then create another
picture either larger or small and use swap picture on rollover of a
transparent giff placed over the picture - just a thought
I have done it with a few of my pictures and it seems to work OK (I don't
have any words on the larger pictures but it would be very simple)
you can view the results here
http://www.ukoutdoorpursuits.co.uk/page_photcredit.htm
On this one I have just changed the backgrounds on the graphic and made the
photo enlargement slightly smaller than the other example
http://www.ukoutdoorpursuits.co.uk/
Good luck
PS - I know "very" little about websites so it really is simple.