There are no hard and fast rules about the pile direction of curtains so here are some pointers to help you decide which you prefer:

Pile up (if you brush your hand upwards and the pile feels smooth, but if you brush your hand down, it feels harsher and the pile is disturbed) gives the colour a richer and deeper appearance and any pile disturbance will disappear more quickly as the pile relaxes and blooms.

Pile down (the opposite to above) allows more light to be reflected from the velvet, so the shade will stay lighter and the pile will stay quite flat and smooot.The velvet will have more of a sheen, and any pile disturbance will show more readily and take longer to fall out.

Cotton velvet is a delicate fabric, the pile can easily be disturbed, but with careful handling and a proper understanding of its nature, products made from velvet can be enjoyed for many years.

If the pile does become crushed, the angle of the pile alters, which may result in areas of the pile appearing lighter or darker in shade. This is often described as pressure marking, which should disappear once exposed to the atmosphere. During this time the pile will relax and lift, improving the richness and the lustre of the velvet.
If any pressure marking continues to persist, a light steaming or gentle brushing in the direction of the pile will also be beneficial.

All velvets are recommended to be Dry Clean Only, to maintain the best appearance of the pile.