Different kinds of paintings quality inspection:

Canvas painting
Oil painting
Silk screen painting
Foil canvas painting
Impressionistic portrait Painting
Watercolor painting
Acylic decoration painting
Cartoon painting
Religion painting
Knife painting
Group painting
Landscape Painting
Abstract Oil Painting
Painting from photo
POP painting art
Framed oil painting
Diamond Painting
Other paintings

Some common factors to check for paintings quality control

Paint cloth
Oil paint
Material
Stretched frame
Gloss
Packing
Workmanship