Please mark openttd-1.3.2.ebuild stable.
amd64: pass
openttd-0.4.2 should be made dependent of games-misc/opengfx-0.4.7. If you're running a mostly stable arch and just unmask games-simulation/openttd, you'll get the "stable" opengfx-0.4.5 and openttd will complain about missing sprites. I first thought it was related to the "gimps not found" message. It is not obvious that you'll need to unmask games-misc/opengfx as well if you want to emerge openttd from ~arch.
Sorry for the typo, I meant of course openttd-1.3.2.