Hi Marco, Karsten

1) 64 x 64 : OK
I think 24x24 should be enough for LoDPI displays, and 48x48 or 64x64 for HiDPI.

2) format : Base64 png
OK

3) 8 Bit : OK
8-bit png doesn't support smooth transparency gradients. We can't make nice-looking rounded corners using 8-bit format.
So we should use 24-bit png ( or we can make smooth rounded corners using png8+html5+js )

4) "function Point() {Point.icon="iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AA...." : OK
function Point() { ... }
Point.icon ="iVBO...
OK

5) Style : flat icons
OK

P.S. Wait.. Does MoI support svg/svgz images? It's a best variant. If not, I would like to advise Michael add support of this format in v.4, and create new MoI interface using svgz icons.
In the nearest future all monitors will be 4k, so vector scalable icons will looks great.
..I'll check it today