Yes, what we are doing is art...at least some of us are ;-) (jk) Does it matter if a painter does or doesn't stretch and gesso his own canvas? Does it make him less of an artist if he doesn't mix his own pigments, or make his own brushes? Whether we build the geometries or create the textures has no bearing on what we make with them. Rest assured, it is art either way. As far as crediting goes; it depends on what the creator requires in their licensing agreement. If it is a freebie, it is a good idea to do it to avoid hurt feelings, most artists require that you give them a credit and a link back to their site. If the model or texture is offered as "Royalty free" or "public domain", then no credit is required. Generally if you buy a model or texture, you are buying the license to use that product to create commercial art. In that case no credit is required. However, if I like a product I may mention it so other people know where to get it too.