Can I use more then one supplier?

The answer is Yes - you can use as many suppliers as you like.  Ideally it would be great to get all your product from one source (less people for you to contact when fulfilling orders), but more then likely that will not happen. 

On several of the product sites that I have I use multiple suppliers.  One I use three for one product site, and the other one I have seven different suppliers because of the variety of the products I want to offer on the site.

Most people fear they will "offend" their dropshipping company if they work with a different product supplier, but this just simply is not the case.  They only care about you making them money with the proudcts they offer and thats it. 

If you ever come across a supplier that will not allow you to sell other types of products on your site that relate (but they do not offer) then drop that supplier like a bad habbit.  By having a bigger catalog of products you will keep potential clients browsing through your site more and give your site more "sticky-ness" to it. 

In conclusion remember that it is never a bad idea to have multiple suppliers and you will never offend your current suppliers by doing so.