Here is a complete guide to creating customized repeating patterns in GIMP and then adding and using them from the Patterns library.

If you're looking to add flair to your images by giving a layer a bit of transparency that fades from completely transparent to fully opaque, GIMP can do that.

Here is a tutorial showing you how to draw pixel art or convert an existing image to pixel art using Pixelize filter in GIMP on Windows PC.