Counts-as Grotesques?

I'm starting up a DE army, haven't decided if I want any grots yet, but I have a few old plastic WHFB Rat ogres I could convert.

What is iconic about grots? How can I make sure people can look at it and say "OH, that is a nice (but hairy) grot"?

Thankful for input and ideas.

For both Wracks and Grotesques, the key thing is they are creations of the Haemonculi. They are mindless servants, usually having been "converted" by a master Haemonculus to either serve as a servant, or as a tool of war.
So whatever the model you use as a base, the basic theme is that they are usually "worked on" surgically, maybe technologically.

Of course you can build however you want, but thats the "Coven" style.

I've seen a few Rat ogre Grotesques, and for inspiration the majority I;ve seen to just mix in Talos parts:

Awesome! I'll probably use that idea if I go for a coven detachment.

http://www.thedarkcity.net/t332-urien-rakarth-haemonculi-wracks-and-grotesques
You could chech this out, even though some pictures are missing, thanks to Botophucket, including my Wraithblades count-as Grotesques which can be found in my project log that is linked in my signature.

I've seen some good ogryn conversions floating around, like those rat ogre conversions they can be made into nice grots with some talos bits.

I'm favorable toward Crypt Horrors with Talos bits, myself. The various Talos helmets and assorted vials/pointy bits slot perfectly onto the Crypt Horror body, so they're a very easy conversion.

I think if you gave them masks and replaced one or both of their hands with crap from the Talos/Cronos kit that would work fine. If you're feeling adventurous, you could also try adding some tubes to their backs.