Some weeks ago, I posted about how could it would be to have the GtkIconView selection looking like this. So, the first step was done: I cooked a patch. I guess when/if the patch is integrated into GTK (I’m still waiting for the feedback from the maintainers), the next step will be to do some rocking theming work in GtkIconView selection. Comments on this subject should go on bug #382544.
Update 1: don’t pay too much atention to this checkbox in this screenshot. This is just part of GtkIconView test program with some weird layouts.
Update 2: for those interested, the rounded borders will come the theme engine, not in GTK itself.