The only screen that allows custom icons on buttons is the roListScreen (see
this blog post for an example). Otherwise you'd have to draw a completely custom screen either with roImageCanvas or roScreen.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)