Can fat be added over visible veins in the temple area?

Fat or sculptra are both great products to pad the temples. Blunt cannulas should be used making the fact that you have visible veins there not an issue. Having said that, not all cannulas and surgeons are created equal. Do choose your surgeon wisely.

Depth of placement of fat grafts in temple area may vary depending of the purpose; large volume correction (in the case of sever temple concavity) may require placement of fat grafts deep underneath the muscle, in the muscle and just above deep fascia of the muscle. More superficial application (to cover superficial, visible veins, is also possible but require good experience and specific type of application. It is best to discuss this option in person consultation with a board certified plastic surgeon with extensive experience in fat grafting. Good luck.

The temples tend to not do well with fat grafting. The area does not have sufficient post tissue to support the graft and most of the fat tends to simply get absorbed possibly leaving fat necrosis. on top of that to technically be able to get fat between the vein and the dermis is probably asking for the impossible. Injecting dilute Radiesse is probably your best option. that works well for the back of the hands.
Perhaps others will have more enthusiasm but before committing to having the procedure I recommend asking to see the providers entire collection of long-term before and after pictures of the procedure.
Best,
Mats Hagstrom MD