Well, Grafx2 was designed with demoscene pixel art in mind. I'd suggest taking that one for a spin sometime. It's all WYSIWYG, supports tons of file formats, and adheres to PCX palette stuff really well, which makes it really handy for PCE art.
The same goes for PSP, and I have a hard time believing that it's inferior to GraphicsGale.
Same with NeoPaint. That tool is pretty effective for the price.
Anyway,
The conversions of high-color backgrounds take a few seconds, with shades of gray. You may not get what you want out of the conversion, especially if you're providing tiles for a multi-screen map.
So, you'd essentially be making more work for whoever is coding the game.
They already have the harder job, so why make it harder?