OpenTTD requires a separate base graphics set to run, which can be downloaded through the installer (Windows) or on first run (Windows, Linux). In case you want to manually download and install it, some options are:

OpenGFX (graphics)

The Transport Tycoon Deluxe data files can be used as base graphics set. You must own a version of Transport Tycoon Deluxe; they cannot be downloaded.

Sound and music sets are recommended (but not necessary). OpenSFX (sound), and OpenMSX (music) can be installed via the installer or - if you own the CD - also the Transport Tycoon Deluxe sound and music.

Additional graphics, sound, and music sets can be downloaded via the ingame content download manager.

Please refer to the readme for more information.

For all binaries officially released by us we publish the MD5, SHA1, and SHA256 checksums. You can use these checksums to check whether the file you downloaded has been modified. All three checksums should match the file you downloaded; if this is not the case it means that either the file didn't come from us or that it got broken during transport. Either way it might possibly contain dangerous modifications and the file should therefore not be trusted!