I don't have a pic handy but I'm sold on my solution:
I got a length of pipe welded to the drawbar. It's a vertical 1.5? inch lump of waterpipe. So I then use a standard bike rack, that normally fits on a tow ball, except that I put it on the pipe AND the rack faces backwards (i..e. prongs towards the car). This works really well.

BUT:
1/ You need to weld to the drawbar (mine is a heavy home-made square section, clearly nice commercial trailers will be different).

2/ The added weight (2 heavy bikes) is significant. I add some luggage items to the rear of the trailer to compensate but this does make it more prone to snaking of course

3/ You need a long enough drawbar so the bikes don't wack the rear of the car when you turn a tight corner

So not for everybody, but if I designed or refurbished a trailer I would build this feature in! cheers JR