The Twaddle v0.21 is up. It now has multiple, user-choosable themes; the current options are the three (“modern”) themes that have already been published - Forest, St. George and Yellow Sky, plus the Default theme, currently Yellow Sky.
I've already created three more themes that have never been published - Mars, Ocean and Sphinx, and I have a nice photo of a sunset from which to create a Sunset theme. A now-revised version of Mars will be made the default theme some time in the coming week.