Change out the trim around the door to a heavier casing and change the knobs to handles. You can also attach trim to the door itself. Then paint.

If you choose to paint them a good amount of prep would be required. I would distress them. Check at local hardware stores for cabinet glaze you may have to get it from an actual cabinet supplier (that's where we purchase it from about $33 a qt and has a black stain look) sand with 60 grit randomly but in the same vertical direction "spot sanding to creat groves in the doors. Then apply some cabinet glaze to a white cloth and run over doors and then wipe clean after about 5-10 mins depending on temperatures repeat as needed to achieve desired color.