How to add new marker types for a TGraph?

I’de like to add marker types to use in my TGraphs - I was wondering if anyone has attempted this already and/or would have any suggestions on the best way to go about this?
Specifically I’de like to make a numeric marker, instead of a square or star for instance it would be a number.
I’de also like to make a variable width rectangular marker.
I’m not 100% clear sifting through the code how the original markers were drawn or made.

For the time being the list of markers is fixed. This is on our “todo” list to add user defined markers (