As we're on a dev forum, many of us here are not 2D/3D artists so our potential games comes with assets that may not be a good match for the design and code.
Maybe, there is a way, if you like little plastic bricks like Lego (there are now many competitors and cloners than decades ago), Stud.io is a great tool to create 3D models using Lego parts in any colors and quantity, as long as your computer can sustain huge models, the tool is made using Unity by the way.


There are many fan websites like Rebrickable hosting tons of models which can be use (with respect with theirs author of course) as-is or as inspiration.
Then you can render pictures using various features and details (realistic or more cartoonish) so the generated pictures can also be used
right away in a game or as templates for pixel arts assets, 3D models or anything else.
Here is an example using a nice Gudi model (a Chinese brand which doesn't just copy Lego models), it can be use for a top/side scrolling shoot'em up or space game, in a cut scene or as something in background in a picture.



(I know, the top view isn't perfectly centered, it's just a quick preview)
Do not hesitate to share your creations 🙂.