Changing your home screen wallpaper is one of the most basic ways to take a Dell Streak and "make it your own." Google is probably the best resource for Android-optimized wallpapers and other great images to hang on your walls, but other phones and tablets often carry some treasures too.
Take the recently unveiled HTC Sensation (previously known by its Pyramid codename), for example. The dual-core phone itself isn't available yet, but its ROM is. Devs are making quick work of it, porting it to other devices with varying degrees of success, and one of the first things to be extracted that will work just fine on the Streak with no root or hacking required is the wallpaper.
Except for the "bokeh" one, which is just standard HTC Sense stuff, all of the Sensation's wallpapers appear to be brand new and—you know it has to be said—pretty sensational. Grab the .zip containing all 15 images (1080 x 960 resolution) at the link below and set them as wallpaper on your Streak. I've got the "color" one on mine right now, and I love the way it looks (even though it has to be cropped).[xda-developers via Good and EVO]