I submitted a new Taskboard update to Apple yesterday. While there are a few fixes in the release, the main feature is custom backgrounds. You can pick any photo from your Photos library. If you're not a good photographer, try some iPad wallpapers. It's fun to play around with different backgrounds. If you have the Projects add-on for Taskboard, you can of course set a different background for each of your projects, and those become the cover photo for the project.
Here's an updated app preview video with a screenshot of the newer feature towards the end. Turn your volume down if you don't want to hear the background music. I forgot to adjust the background music levels for the video, so I'll likely fix that in the next version of the preview.