RevoStock has everything! Still backgrounds, video backgrounds, sound effects, music, and special effects. It's a huge library of user generated material, so there's a wide range of different styles. 

You can buy credits and then use them to download the items you want, which range in price from $3 to £15, so it's all pretty reasonable. 

Better still - you can upload you own material and share it with other users, and then enjoy making some money too when people download your material.