I had the same Idea. If a sites membership is like that of Joomlapolis just think how impressive it would look if you could display hundreds of avatars on one page.
I actually made a content page called "wall of members". I resized the avatars about 1/5 of their size (really small) and then put the links to the profiles in manually.
I was thinking about hiring somebody to code something to do this for me in the future.