An incredible gallery of 16×16 pics for Gameframe (link at bottom):
700 “people” in the standard Super Mario Bros. standing pose.
You can download a ZIP and then convert the JPGs into Bitmaps. A batch converter like XNConvert will help you a lot. I will not post my conversions here for copyright reasons.
Hints: Cut from 500×500 to 400×400 by taking 50 pixels off left right top bottom.
Scale from 400×400 down to 16×16 (divide by 25)
Increase brightness SLIGHTLY – due to the JPG compression you will have some whites (255,255,255) that are 255,254,255 or so – by increasing brightness they all will be 255,255,255
Replace 255,255,255 with a dark background colour. Dark red for horror motives for example. They look MUCH better on Gameframe if they are NOT on white backgrounds. NONE of the artwork uses 255,255,255 in the actual figure, so direct batch replacement of 255,255,255 is working well!
I made a couple of topical folders like Harry Potter, Horror, Futurama, Flintstones & Smurfs, etc.
My absolute favourite are Daft Punk, Magnum P.I. and many of the Marvel/DC characters. The guy is a GENIUS in packing all the info you need to identify a sprite into 16×16 pixels.