I've been lurking here for a little over a year, greatly enjoying everyone's artwork, and decided that perhaps it was time to jump in and put some of my own personal work out here to see what I can learn. I am a professional astronomer and hobbyist artist, although my artwork has been widely published. I'm primarily an astronomical artist, with a deep personal interest in exoplanets. I'm not a matte painter per se, although much of my work uses a lot of the same techniques. Hence my interest in this site and in learning from you all.
I've seen several of you use 'mouse overs' or 'roll overs' on your sites to compare your final pieces with the original plates and I really love those. It inspired me to add such a gallery to my own page in prep for my introductory post here.
http://www.3dimpact.com/
Navigate to the "GALLERY" section and my 'Digital' and 'Mouse Over' galleries to see my digital art. Some pieces are 100% 3D, some nearly pure Photoshop, and some digital 'matte paintings'.
Here are just two samples to introduce my work:
Final piece ("Beach 1")

Original plate
Final piece ("Desolate")

Original plate:
I'll update here in this thread as I generate new pieces with appropriate digital matte painting techniques...
Dan