Schematic: quite easy
VGA mode used: 640x480 @ 31,5kHz/60Hz, (virtual) dot clock 25 MHz, visible information per line: ≈ 80%.
Bitmap size displayed: 128x120x4 (every pixel is a rectangle of 5x4 dot cells), using fixed DOS/Windows/CGA palette. When you clone this, pay attention to copyright issues for your picture when you choose one yourself! However, this construction, firmware, and test pattern has BSD lisence.
The quartz crystal frequency is only 20 MHz (the ATmega88-20 is not overclocked). All components are available at Reichelt. The optimum microcontroller would be ATtiny84-20.
This PCB design (Eagle, SMD) for usual nine-pin SubD adapters uses a plug and a socket, so you have both genders readily available.
Population of this two-sided, 1 mm thick PCB
Freeware, open-source, you can use it for what your want, even commercially. Keep a copyright notice when you use this project with small or no modifications.
Here you see my test bench, and how it works