i think, if you feel the need to do abstract, you should just go and do them.
but i understand what you mean.
for me abstract is the most difficult to do.
and it def needs drawing knowledge/experience.
i dont mean that not amazing things can happen without that knowledge and work underneath the painting, but with it, the amazing things happen with more depth and can be more a result of your choices and not luck or your inner reflecting on the painting alone.
take franz kline for example. these arent just black and white lines. no way.
in your painting, the right middle part, blue, yellow and black is good.
and from the faces, i like the 1st one the best.