I decided to make this retro-style tileset using the classic 16-color EGA palette that many old DOS games used back in the day. It can be used to build temples, castles and the like, although it also has a few outdoors elements (intended mostly for backgrounds).

I made two matching sets with different colors for the wall blocks, and a similar retro-style night background to go with them. Below are a couple demo pictures:


A few notes:

The stairs can be climbed just by walking/running.
The torch/lamp thingy is designed to work with the small flame (Bank#8 Obj#8), and the bonfire is intended to be used with the big flame (Bank#8 Obj#6).
The light/shading tiles have an invisible square collision mask so they can be put in layer 3 over any wall tile (or anything else you want to be treated as a solid block) without having to add invisible objects.
Fun fact: If you use KS+ and slap an AND tint with the color set to light gray (#808080 hex, 8421504 in decimal) to your screen, you'll get a less detailed and more posterized version of the set, resembling the default color palette of the ZX Spectrum microcomputer.

Feel free to use/remix any of these graphics for your own retro-themed levels. I'll probably make some edits/tweaks and release an updated version in the near future, so any ideas and feedback on how to improve this set will be more than welcome.