Given that he was a man of very high station, Kagrenac would most surely be portrayed by an artist in the most respectful and flattering manner possible. Flowing, highly-detailed robe, decorations demonstrating his rank, ornate jewelry, all that stuff. He may even be wearing a bit of armor, like a pair of boots and pauldrons. For this statue, what I most want is for him to be wearing a belt with Sunder and Keening dangling from it, and Wraithguard covering his right hand (who knows which of Kagrenac's hands was dominant, I'm just going with what hand Wraithguard normally goes on for the player). The Tools are what's going to give evidence of the statue being of Kagrenac, given that his appearance isn't exactly as recognizable as that of, say, Vivec.
I envision Kagrenac being a rather nasty-looking fellow, a little scarred and deformed from magical experiments gone wrong in his youth. His history would indicate to me that he didn't spend much time smiling, at least not while surrounded by people. I imagine this would be a little difficult to have come through in a chunk of stone meant to look almost 4000 years old, but perhaps the statue doesn't have to be made of something so susceptible to the elements?
I don't know what I could do to reward anyone willing to make this statue for me, but I'm not without skills, so I'm sure we can work something out.