If your clown is very new to your tank, I would suggest letting him get used to it for a week or two before trying to get him to host anything. If he has only been in there for a few days and stays near the glass, then he just needs to get used to the tank. I think its great he is tank born though, he will be very active and not so fearful of the tank as a captured clown.
I dont have any anemones in my 24 gallon (they require pristine water conditions and very expensive lights) but my clowns have hosted lots of corals. My male has hosted a bubble coral, fuzzy mushrooms, a frogspawn and some xenia.
Oh, and the picture technique is supposed to work (but like I said, dont freak him out with a picture if he has only been in the tank a few days). You just tape a pic of a similar looking clownfish hosting an anemone and they figure it out! Good luck!