Hm... I don't actually know of any good galleries and websites with a lot of HQ images for artists in general since I also rely on Google and Last.fm a lot but I do know that if you're looking for something specific, then checking fyeah tumblrs or fan sites for a certain artist might be a good place to start. I know EXO fyeahs have A LOOOOOT of images and the tags are really helpful to find what you're looking for, plus they post literally anything relating to the artist but I don't know how good other fyeah's may be.

When I'm looking for images from a certain photoshoot I usually Google the artist name + the name of the photoshoot (and any other name variations that it might fall under) and just scroll through pages until I see pictures that match the photoshoot. Sometimes click on the website where the image came from may lead to other pictures from that same photoshoot that the same may have posted but it depends.

Hopefully these suggestions can give you some ideas on where to start? It might lead you to other places that will help you but this is about all I know and use so I'm sorry if it wasn't that helpful!