Hello! I have made/collected/purchased a lot over the years, and even on stuff I buy I also often end up often doing modifications, extensions, color swaps, etc (assuming the license allows it), and for that I use https://dacap.itch.io/aseprite for it.
A large portion now comes from or is based on tiles by https://pita.itch.io, which is really great and straight replaced a lot of my older stuff.