what do you call this type of short memory test?

It's an episodic memory test of short-term visual recall.

Episodic & visual because it's pictures (would be a semantic test with words). Recall because you don't give participants any cues when they do the recall phase - would be a recognition memory test if you gave cues.

I dont think the test actually has a name. They are usually just called memory tests or spatial tests but i found this on wiki;

http://en.wikipedia.org/wiki/Mnemonic

(Mnemonic tests can be visual)

As for a long term memory test on a massive sale, google 'Professor Robert Logie'. He was involved in the largest ever memory experiment.

ugly