I like the recent addition of theme packs, but I'd like more variety. I like the simplistic, minimalist default (purple) theme, but I wish I could choose different colors.
Themes is a feature that no other streaming device supports AFAIK; it is one of the main reasons I picked up a Roku.
I completely agree that the theme packs are what sets Roku apart from the competition but if you look you will see that the theme packs have basically been static for 6 months or more. There are wallpapers offered occasionally but they are quickly taken away with no explanation as to why they cannot be permanent. In the 10.5 tips and tricks update Roku even mentioned the updated themes but their valued customers know that there are no updates to any of the existing themes and those existing things are far too few.
The new dynamic wallpapers are a great addition to the other great improvements that Roku has made to their operating system in the last year or so. Please bring more themes with sound and screensavers! Loving the improvements!