Website Product Thumbnails

I need some product thumbnails created for my website. I will do in a few stages. stage one will be 91 thumbnails. I will provide 4 different colourful backgrounds that I want the product to be on. The product photos currently are either on a white or black background (a few are on a model but on skin) so it will be very easy to remove the current background and onto one of the 4 I will provide. Once on the new background, drop shadow to be added. The ,majority of products come in 2 colours, so I would want both colours added to the same background, This isnt a project you need to do too much retouching really. Mid next week, I will have about the same amount of new products to have the same done to them. This is cheap and fast moving product so the life of the thumbnails will not be long, so not looking to invest a huge amount into it.