Here’s are some simple background images with colorful gradients. The images are in 4K 3840×2160 resolution and horizontal 16:9 aspect ratio, suitable for use as high-resolution computer wallpapers besides background image for your own digital content. You can also rotate them to get vertical 9:16 images suitable for phones.
The images are in the highest uncompressed .png file quality.
If you want to make gradient images based on your color choices, you can use this mini web app I made: Gradient Image Generator.