There were three artists who created the first twelve Mini-Toons. The third didn't participate in the next twelve. If we call them "A", "B" & "C", then it's quite easy to tell them apart. I can confirm that "B" was Peter Archer, the creator of Action Transfers.
From these first twelve, "A" was responsible for numbers 1, 5, 7 & 9, as indicated below [in square brackets].
"B" (Peter Archer) was responsible for numbers 2, 4, 10 & 11.
"C" was responsible for the rest. So the three different artists each had four sets — which was neat.
Personally, I regard Peter as much the finest & most suitable artist for the Mini-Toons format.
It's also interesting to note that some of the backgrounds are in 'portrait' format (taller than they are wide), although most are 'landscape' (wider than they are tall).
The transfers sheets are held in place by being inserted into a crescent notch. This is, in my opinion, a better method than the later staples, since although it does affect the backgrounds slightly, it doesn't risk damaging the transfer sheet.
Picture Credit: The SPLAT Scan Archives
© Tom Vinelott 2016