Yes I do have all the rights and no it is not in PUBLIC DOMAIN .
By using their elements of stock owners I take resposiblibty to use them with their rules. I give credits to them and let them know how I proced with that image. Is it commercial use or not.
More then that. Creating image like my is orignal artwork on its own and I am owner of copyrights of that image. How I did it . Did I use collage or any more modern form of collage is not really just mix. You opinion on how it is "just mix" is yours and not very nice but it is just opinion and it is not law.
Any and all rights violation of my creations will be agaisnt international laws about intelectual property and more important for you against deviant art rules.
Any modifcation without permission is against the laws.
Any commercial use is againt laws.
PUBLIC DOMAIN means free of copyrights after something like 125 years of author death. So since you are not any law enforcer or stock owner you can not say that I have no right.
I have all rights but you on the other hand on your profile have a lot of images created from other images without even credits. Probobly becouse you are using images that are not in the stock section on deviantart.. maybe from google images. Wich might be violating some copyrights.