The solution was pretty easy, but I overlooked it:
QBrush bgBrush,fgBrush;
bgBrush = QBrush(color);
fgBrush = QBrush(pixMap);
painter->setPen(borderpen);
painter->fillRect(rec, bgBrush);
painter->fillRect(rec, fgBrush);
painter->drawRect(rec);
Just a brainfart from my side, nothing to see here. Move on!