If the background is not isolated, it should be maintained clean and spotless. It should also be consistent and bear no banding or any other abrupt color shifts.
Skin defects such as pimples, spots, blemishes, stretch marks, bruises,
Palms, knees, elbows and heels should not be very dark, red or wrinkled. How perfectly they should be retouched depends on the particular store demands.
Shoes should have a perfect fit, no matter if they are too small or too large for a model.
Hair should be tidy, no stray hairs or loose strands if it's not on purpose.
If a label is ought to be removed after purchase, it should be removed from the image as well.
Suits, jackets and coats sometimes have stitched sleeves, pockets and other parts of the garments. This stitching should be removed.
Sometimes shoes are taped during the shooting to protect the soles from scratching – this tape has to be removed. If it's time-consuming, more care and attention is expected from stylists or whoever tapes the shoes
Excess wrinkles and “bubbles” on clothes should be removed. However, the question how many wrinkles and how thoroughly they should be removed doesn't have a single answer. In some online stores the left image would be totally fine, while in others it would not be tolerated as too wrinkled.

If model’s underwear looks out of place, it should be removed.

Female nipples are usually removed.
Armpits should not be wrinkled and dark. Doesn't matter if it's natural or not, it's just another harsh standard of the industry
Skin should not be heavily blurred, overall or locally, especially locally.
No labels should be visible under clothes.
If a pose is static, the garment is expected to look symmetrical

There's no single approach to plus size models retouching. Some online stores prefer a more natural look (to the left), while others go for flesh-cutting heavy-blurring retouching methods (to the right).