large mods to the exterior such as paint color or rims tend to hurt the resale value, as only a select number of people will find those mods acceptable. People driving common cars such as civics tend to modify cars in outrageous ways because they're trying to differentiate themselves from the million other civics out there and personalize their car. With cars like the slk55, there's far less "need" for crazy mods such as huge wings, stickers, colored rims, fartcan exhaust, etc.
As to this car, to me, the matte black looks good. colored rims, not so good. Hard to match colored rims to the car in an aesthetically pleasing manner. And it does look odd... Probably the only color type that wouldn't look too odd on a black car is black rims with metallic outline on the rim. If the car was colored, you could use a similar color outline instead on the rim- red/yellow/etc. A straight colored rim tends to be too overbearing, espeically if it doesn't match the car color.
these were the results of a quick google search. something like this.
Personally, I dislike most aftermarket rims, probably because they tend to be too flashy for me. But to each his/her own. Just too bad he didn't keep the stock rims and install aftermarket. That way, at least he could give any new owner the option of returning to stock.