One of the many reasons to install a custom rom is the ability to run a custom theme. There really aren't very many Roms left out there that have theme support specifically for their rom. Most themes these days are built for the CM12 theme engine, overlay, or for custom launchers. Team Venom has a full thread filled with all kinds of custom themes built specifically to be used with the ViperOneM9 rom. This includes full themes, icon packs, status bars, boot animations, and wallpapers. Check out the thread below to see what is available.
via XDA