Hmm... try doing more 'fluid' hair outlines, that is, less solid borders, with hairs making it uneven. Then colour it in slightly less stark colours, if you want similarity with this particular colouring. Else, just adding more various small strands without detailing them much would work well. I think.
And well, the sketch does its job. I'm sure you'll get some background done fully soon. Until then, I guess you could limit their scope, so that you have less to finish.
Just thinking aloud... well, a-type.