I discovered a novel way to create an iMovie background just this morning (I think it is as Google showed no one describing this method, but I will stand duly corrected if someone already has!). I wanted a wallpaper-like background with a repeating motif and I found BgPatterns, a web app that makes wallpaper for websites or your computer screen if you wanna. It’s free, no worries.
Once you get on BgPatterns, you basically choose a motif and then play around with the colours for the image and the background. The texture of the wallpaper can also be altered, as well as the orientation of the repeating motif. Once done, you can simply preview the wallpaper and save the actual block, but not the entire wallpaper.
Now is when you have to do a bit of work.
Set this image as your screen desktop (‘Set desktop picture’ for OSX), make sure it is tiled (go to ‘System Preference’ for OSX), and simply print screen it (shift-cmd-3).
Then open the saved image from the print screen on Photoshop. As my iMac has a 2560×1440 reso, altering its dimension using ‘Canvas size’ is easy. In this instance, as my vids are in widescreen for DVD purposes, altering the canvas to 1280×720 would suffice. Save the completed wallpaper for your background on your next iMovie project.
Once on iMovie, drag the wallpaper onto wherever you want on the timeline in the iMovie project you’re working on. I would opt to ‘Fit’ the wallpaper and not use any ‘Ken Burns’ effect on it and, voilà, your new custom iMovie background!