Is it just a "raw" display, so that your processor has to do all the pixel-level drawing stuff?

In that case, it would probably make sense to have a separate display processor to do all the nitty-gritty pixel-level stuff, and define an interface with higher-level commands such as "draw text", "show icon", etc.

I have just seen a demo of this: http://www.synlinktec.com/
It's a graphical display/HMI with processor that communicates with the microcontroller over a simple UART command link

You set-up the screens with a PC tool, and the microcontroller then just sends commands as required.

I don't know how it fits with your budget - if it's too expensive for you, you could form your own based on the idea...