Are you building a portfolio or a gallery with WordPress? If yes, it can be a good thing to randomize posts order, just like I did on the footer of WpRecipes.com theme to display WordPress themes. That’s very easy to do with WordPress: Just read on.
To randomize posts order, you’ll have to use the very powerful query_posts() function before your WordPress loop:
query_posts('orderby=rand'); //Your loop goes here
Of course, it is also possible to randomize only a certain category:
query_posts('cat=10&orderby=rand'); //Your loop goes here