BRIX is a project with goal to replace every single sprite that the base game uses, to eventually form into a base set.
Right now it is in development - first it will be released as a NewGRF, until it gets all of the sprites necessary.
All sprites will be in x4 zoom in 32bpp colours.BRIX 0.0.1 will be a NewGRF which replaces:
- bridges, tunnels, road crossings
For more info you can read in links down below