Hi! I see someone else already volunteered as a musician and artist, but I thought I'd also offer myself as a pixel artist. I can send you samples if you like, and I recently uploaded a game for a game jam that utilized handmade pixel art as well (that game is all simple small scale stuff, but I have more detailed work on my computer)
Viewing post in Unity dev looking for artist and /or composer.
My idea when I was wanting to go solo was going to be a top-down puzzle game where you have to push blocks or collect some sort of items in order to "fill a space", perhaps a big hole, that would allow you to progress to the next level. I hadn't started it yet, just the player controller. You're welcome to borrow elements of that if you'd like