Greg Rutkowski is a freelance concept artist and illustrator from Poland, whose clients include Wizards of the Coast.
Among his other fantasy subjects, Rutkowski paints terrific dragons, with a feeling of leathery textures and lots of creative variations.
His digital paintings often have a nicely naturalistic and textural painterly approach. In addition to his concept pieces you’ll find digital paintings of landscapes in his online portfolio and deviantART gallery.
Rutkowski has digital painting tutorials available through Gumroad, along with downloadable Photoshop brushes. You can find previews and other videos on his YouTube channel.
He also has prints available through deviantArt, and (larger, if I understand correctly) through Displate.