I'm not really an artist (primarily a game designer) but I have to do everything myself. And while I tried drawing vector graphics, and got decent results, I stick to pixel art as it gives similar results in shorter time. It was especially important during this game jam, as not only I've been working alone, I ended up having to finish my game in less than a day. Which is also why I decided to make player character a slime - slimes and swords are two things that I drew so many times that I could probably do it again with my eyes closed. I use gimp, mostly drawing one pixel at a time, occasionally helping myself with some filters (lately I've been using RGB noise a lot).
An interesting problem that I encountered while working on sprites for my game was the fact that I drew them with black outlines. And since it takes place in space, the background was mostly black too. Not wanting to redraw the sprites without outlines, I changed their color to light gray, which turned out surprisingly well.
You can check it out if you want to: https://itch.io/jam/gmtk-2019/rate/462343
Yeah I figured out that working on background and character art simultaneously makes quite sense - or at least setting yourself a colour code for everything and see how it machtes/contrasts before you start making the actual art. :)
I build both my background and character and items next to each other and always put them on the background to see if the contrast was enough and if the colours matched!