Specifically for pixel art related to making games, having a tileset editor that uses a grid to split an image into known segments would be helpful. With the idea being that you not only can draw on or across these segments, but also a mode or pane where you can select the tiles and place them in an empty grid to see what they look like next to each other (like if you were placing them in your game). Pyxel Edit is definitely something to reference for great features, but I think I prefer how LightCube has implemented it. I do not think the way Aseprite or Pixelorama work with tilesets is great, you end up with a jumbled list of tilesets. Tilesets should stick to a static grid and each tile selectable to be copied to the composer pane. This has to do with the visual structure of tilesets, as they are often drawn next to relative tiles.
Thanks for the proposal. We actually have plans for tilesets.
If you want me to include this proposal on the website, please improve formatting and take a look how other proposals are written down as this has too little info.