You gotta have cute theme anywhere you can, right? ;p
I always change up my wallpaper everytime I got bored, but I change up the whole look of my phone (custom-full-themed) only every 5-6 months or so, because changing every icons in your phone actually takes time than you think it would. Especially when I want them all to be color-coordinated and each one must have a continuity / similar theme with the others.
I'm using iPhone so I'm not sure if this app is also available for android or not. I use Cocoppa app which enables you to make cute shortcut icons on your dashboard. It has so many cute and pretty style icons (as well as every style you could think of; from emo-style to masculine to robotic to sanrio, etc) that you can choose from.
The icons are users-generated, meaning that they were created by users and lots of them can be used freely. So if you got what it takes you can also put your icon designs in Cocoppa, I've seen a couple of designs from Indonesian users and they are very talented.
Although Cocoppa takes up memory bytes and it makes my phone slows a bit, but I still gotta have them in my phone. It bring smiles and happiness to me everytime I open my phone ^__^
This time my theme is "purple" :