I came across this image some time ago and it does look in 13th century style to me, but I can't find any source for it anywhere. Does any of you know where this picture comes from and if it is really a 13th century image or done later in 13th century style?

Seems like a modern drawing.

Look like Maciejowski Bible but might be modern art.

The background of the picture (the lozenges and dots) stands out to me mainly. A medieval artist, I think, would have tried to make them far more uniform than they appear here.

Apart from that there's nothing that stands out as blatantly wrong to me...

This reminds me of the work of Dan Escott.

http://bearalley.blogspot.com.au/2009/12/dan-escott.html

Almost %100 sure that this is modern. Pretty cool though.

The largest image online seems to be at the following site. You could always e-mail them and inquire what the source might be.
http://stjj.org/

It's certainly not medieval. The crosses on surcoat and mantle are overblown,
[ Linked Image ]
[ Linked Image ]

The medieval practice of showing someone holding a small church or other building usually indicates they had it built.

I think it's a pretty good modern pastiche of medieval art, but the artist tries a little too hard -- the shadows on the knight and his cape are too detailed and realistic.