Rainlendar is a self-described ‘feature rich’ calendar for your desktop that allows for extensive customization, tweaking and personalization.
Events can be set with an alarm for notification and the to-do list makes a handy extra.
Rainlendar is available in a free ‘lite’ version or as a ‘pro’ version for €9.95.
Find plenty of weird, wacky and wonderful themes all over the net, but DeviantArt is a particularity good place to look.
The free ‘lite’ version as well as the pro version are available as .deb installers downloadable at: -