~ possibly add fifth wheels like Brian Epstein, George Martin, Yoko Ono , Linda McCartney, or the children of theirs,
~ psychedelic type image would be one good idea, though you could also do earlier suit and tie drawing or later post 70′s drawings,
~ you could do b&w sketches, water colours, or pastel,
~ this time of year, you could add christmas flare to drawings,
~ you could do an age time-line of each member,
~ you could try changing perspective of their pictures from how you would see them today and yesterday,
~ you could ad sounds and lights to posters,
also mix those and other ideas in a combined poster set, and have fun,☺

fd’s Flickr Toys
http://www.bighugelabs.com/flickr/
U.R.Celeb – create your own Magazine Cover
http://urceleb.oniton.com/
Blibs LunaPic
http://www14.lunapic.com/editor/index.php?action=undo
AndreaMosaic,
http://www.andreaplanet.com/andreamosaic/
Photofiltre
http://photofiltre.free.fr/frames_en.htm
..
References :