Here's some good info on SDA : http://www.rodentfancy.com/rmfe/virus.shtml
There's a pic too.

I couldn't find any pics of rats with mycoplasma. But it's fairly easy to diagnose from just noticing the symptoms. There might be some porphyrin (red discharge) around the eyes and/or nose, wheezing, sneezing, difficulty breathing, tiredness, loss of apetite and thirst, erect fur, etc.