The wonderful thing about standards is that there are so many of them.
The closest thing to a standard is, unfortunately, for LCD panels that have controllers but no drivers. IIRC, a typical interface will have signals for phase polarity, frame clock, line clock, data clock and 4 data bits. Every line of pixels one should clock in enough groups of four pixels to fill the width of the display (extra bits will be ignored), driving the data clock high and low for each group. The drive the line clock high and low to strobe the line. The first line of each frame should have the frame clock high, and the phase polarity signal should toggle every frame.
The line clock signals, and those derived from them, must be sent at a uniform rate. The precise timing of the data clock signals, however, doesn't matter provided that all the clocks happen for a line happen within the proper window. If you don't have DMA, it may be possible to keep a small display happy and still have time to do something else, but refreshing the display will be a pain. If you do have DMA, however, and can manage a small CPLD to handle a few aspects of the timing, implementing the display that way may be very rewarding. I've done a display panel like that and achieved display-update performance superior to anything I could have done with a conventional display controller. I even achieved 4-level gray-scale by running the display at 100 frames/second and, every three frames, driving the display twice using one buffer and once with another.