Here's a graphical VFD screen (from Noritake) that I found while cleaning out some boxes at home and lined it up on a spare interior vent / ash tray panel. It's controlled by a fairly simple and documented interface and VFDs are great in cars: they're easy to read in virtually all types of light and they work well through a large temperature range. They also have a cool vintage look to them, they're what you often see on a high-end stereo.
I'm thinking of hacking up a quick MCU-based control board and reading some basic sensors along with a battery meter. A button or two should suffice to toggle between readings and the MCU could even chose to show a particular reading and make an alarm when that value is critical (ex: low oil pressure), just like it's done on some new cars.
This particular module is about the right size for the ashtray cover area, it would just need a nice wooden bezel done with a matching veneer for the "roots" trim I have here.