The iPhone 6 concepts of course started appearing even before the iPhone 5s was launched, but now that the new handsets are old news, the concept bandwagon is gathering speed.

Apple is known to be testing a variety of handset sizes, but has always said a phone should be usable with one hand, which rules out any of the more tablet-like sizes out there. An obvious way to increase the screen size without greatly increasing the external dimensions of the phone is work on reducing the size of the bezel.

Apple already did this with the iPad Air (though in that case to reduce the dimensions while retaining the screen size). That’s the approach we see in what I consider to be one of the most realistic concepts out there …

Mechanical engineering student Nikola Cirkovic put together a series of renderings of a design very similar to the iPhone 5s, but with a near-invisible ultra-thin bezel at each side. Possibly a little thinner than might prove possible to manufacture, but certainly along the lines I’d expect Apple to adopt.

The gallery shows both Space Gray and Silver models, but no gold. I like the fact that Cirkovic has resisted the temptation to get carried away. The larger screen size and thin bezels aside, it follows all the design cues of the existing phone.

Then we get to the dumb concepts. Three different sizes …

A curved screen with the curve the wrong way, maximising reflections and leaving the vulnerable screen facing out in your pocket …

The iPhone 3GS revisited …

The just plain weird (ok, he wants to project a keyboard onto the desk, so there is the semblence of method in his madness, but still) …

Bonus points for a concept that would make the phone unusable in landscape mode, turning the whole of the base surface into a touch-sensitive home button …

I didn’t think the concepts could get much dumber than this …

But it turns out I was wrong:

(You won’t believe how many variations on that there are out there.)

Seen any worse ones out there? Post the links in the comments …