I think it was Wordsmith who posted about Wilder one time not too long ago, and I was surprised that I kind of liked it. I guess because it makes me think of Almanzo Wilder, and who didn't have a crush on him?! So it has that sort of feel, which is my favorite kind of name. That earns it some bonus points.
I think with
Caspian, Wilde fits much better than Wilder. Wilde is sophisticated and a bit quirky, perfect for
Caspian. I'd probably make sure you were an
Oscar Wilde fan (or it was a family name) before using it, though.