32bpp Extra is an open source 32bpp replacement for the 8bpp sprites that were not present in the original Transport Tycoon Deluxe (TTD) graphics but were added to the game by the OpenTTD developments.
For 8bpp, these graphics are available in 3 variants:
-in openttdw.grf (original_windows option in the game options screen)
-in openttdd.grf (original_dos option in the game options screen)
-in ogfxe_extra.grf (opengfx in the game options screen)
To replace the 8bpp graphics with a 32bpp set that is compatible for all 3 groups of users, the 32bpp Extra projects provides:
-a 32bpp_extra.grf that provides the base for the 32bpp sprite numbering, usable both in the default and in the patched Extra zoom level version of Openttd
-a set of 32bpp pngs at default zoom level, to be used with this grf.
-a set of 32bpp pngs with extra zoom levels, also to be used with this grf, but icm with the patched version.
The project is still in it's startup phase, but a repository with the possibility to generate the newgrf is available at the second link.
Automatic bundle (tar including the newgrf) generation on the server, and a download location for it can be found in the first link. Unzip the file in your [Game directory]/data directory (no need to untar the resulting tar).