Mozilla has released the Personas add-on
for Firefox Mobile, allowing you to install any of the hundreds of lightweight themes available at getpersonas.com
. While there's not much chrome to theme on Firefox Mobile, there will no doubt be plenty of users who leap at the chance to customize its interface. Your Persona will appear in a few places: on the Awesome Screen (which appears when you tap in the address bar), on Firefox Mobile's tools panels, in the Form Assistant, and in the Find in Page dialog.
If you've got Firefox for Android installed, just hit the add-ons page and check the recommended add-ons at the bottom of the page -- Personas should be listed there. If not, just search for it and install!