That's what I knew as well, but during the last build contest I saw many decorative heads in one user's plot (I can't recall whose) and he told me that they were his heads and that he just did what I described in my comment earlier. Sadly I can't recall whether there were different head-skins involved in the plot and in any case I didn't test any of this myself. That's all I know (not very reliable information, I admit).
When did you do your last tests?

 

I like this idea, adds some fun to simple decorating. i need something new to replace the poppy on my coffee table.

 

+1000
Cool idea, would add a creative touch to the server:)

 

+1 Very good idea, would make builds more creative and unique.

 

+1 This idea could always be done by using a skinstealer and doing /skull, so the price may have to be not as high as 10k, or about 20 nstars. But great idea! I would love to see this being implemented in my favorite server!

 

However it might not work:

 

you can actually set custom textures for heads, unrelated to accounts. (at least, it's possible in bukkit)

 

How so?

 

It makes use of a base64 encoded data url. So you can literally use any image you want for player heads.

 

But that is presumably going to be much longer than 100 characters, so how can you possibly enter all that information in a single command without command block access?

 

The server would have to create the heads and name them for individual use. Or release them in packs like a kit.

 

LOL I don't understand the original comment, nor the first edit, nor the second one

I see... but then only the few heads imported by staff will be available to us, thus limiting our choice; and it would add a burden of work for staff if we want the catalog to grow in the course of time. (I know this is no different from the original suggestion, however I was hoping something more user-custom was possible)