I was wondering if you guys have thought about open sourcing the art/graphics of the game a bit.
By this I mean letting people, from an early stage, contribute with airplane textures, car textures and so on. You could provide some specs (resolution, file format, etc) for the textures you are using and in need of and then the community could hop in and post suggestions here in the forum (or somewhere else). Other people could then vote on their preferred textures or even improve on them and make new suggestions.
I understand that for most graphics you probably want to keep the looks consistent and according to your creative style, but I think that for things like airline liveries, train liveries and so on the community could help you out a lot and provide a great many ideas and even save you some work on designing/drawing/editing.
As compensation (if there even would need to be compensation other than helping out), you could include contributor’s names in some about page or credit sequence.