How to generate a composite video
Actually, using a suitable micro you could get 12-bit colour and reasonable resolution.

For example, the STM32F407 has two 12-bit DAC's that can be continuously loaded by DMA to generate composite video.  Allocate a section of RAM (it has 200kB) to be a frame buffer, fire up the DAC and DMA and off you go - reasonable video from an MCU for zero CPU cycles.  You can get an STM32F4Discovery board for US$15, including an on-board debugger, and the free Coocox IDE is pretty reasonable for what you pay.  For another $45 or so you can add a base board with an Ethernet port and an SD socket for image upload.

Just a thought.