Board Thread:Support Requests - Getting Started/@comment-28931162-20170325232851/@comment-9605025-20170326074915

It depends on the level of detail you want. Common ones I have heard of people using are Gimp, Photoshop, and Paint.net. However, if you just want something that will replace large areas of single color such as a background sometimes MS Paint (different from Pain.net) or even MS PowerPoint is sufficient.