Windows only: Maybe you don't have time to create gradient colour fades, embedded calendars and interactive clocks into your desktop. SE-DesktopConstructor is a simplified desktop configuration tool for those who aren't in need of every widget there is.
The options in SE-DesktopConstructor are far fewer than in a full customisation suite like Rainmeter, but they're just enough to make some good-looking desktops. Pick a background image, choose a colour and graduated fade level, position some graphical boxes, then place a clock or calendar. With just a bit of practice, you'll have a desktop set up that you'll dig. SE-DesktopConstructor has to run in the background — it took about 13MB on my system to run, but your mileage may vary.
SE-DesktopConstructor is a free download for Windows systems only and comes with a no-install portable download option.