I think Spiderman is a copyright design and therefore there may only be a few vendors that sell the legal designs.
Even if there are websites that sell Spiderman Designs they are probably not legal designs.
Only large companies such as Brother or Dakota Designs have contracts for designs like these. They pay a large licensing fee to the copyright holder to be able to digitze and sell the designs to the public. They only sell these types of designs in sets not as individual designs.
Most Cartoon Characters and TV Show characters come under this category.
So be very careful if you find the designs.
I believe the 3 links to websites that one of our members listed here for you are selling illegal designs.
EastWitch2
I bought a few designs from www.needlework.ru (Disney Cars Designs). They are quite dense but they stitched beautifully (the registration problems I had were me not having enough experience and not stabilizing enough)... I just assume they were legal. Disney is quite protective of there rights, they wouldn't be in business if the designs were not legal.
They are selling illegal designs.
Just because they sell them dosen't make them legal
They do not recognize the copy right laws in the country they are in so they think it is okay to sell the designs but it is not.
They very likely do not have a license from the copyright holder to digitize and sell the designs to the public.