I do have bigger version. I actually tried making wallpaper out of this. Here is link to it: [link] I can also upload the original scanned versions (2400 x 3400 px) of these pics to my stash, if you want to try making your own version.
This is the most incredible piece of Dawnguard art I've seen! I just love how you have portrayed both sides of the plot, and how Harkon still looks as powerful and intimidating (if not more so) as Isran despite being only him and the Vampire Lord. Brilliant work!