I was hopping this topic would be about the future. What you want to do was done years ago with AVR Arduinos.
Hope Graynomad contains his laugher and I am sure he will. He is a gentleman.
Just buy an Adafruit Wave Shield and use my old WaveHC library or WaveRP library. WaveHC can play 16-bit 44.2 ksps files. The DAC on the shield is only 12-bit for cost reasons but Ladyada did a great job for the low price and the sound is good.
WaveRP can record 8-bit 44.2 ksps audio using the AVR ADC.
My binaryLogger sketch can record 8-bit data at 90 ksps and 16-bit data at 45 ksps using Microchip ADC chips.
My SdFatRawWrite sketch can write to an SD at about 500 KB/sec. This uses 100% CPU but at 250 KB/sec you have 50% cpu to generate data. This should do for your image data.