For me I got the direct impresson from her that if I put one of those on my body or recognized it she would show me what pain really was. Now if I wanted to use the combination of Keys, Knife, Y and dice that would be fine. In fact as soon as I get it just right I shall have it done.
I used that wheel symbol when I made my second portrait (among many) of Her and i didn't get the any particular wrong inkling. Of course, the symbol was actually a very small detail of the picture and this was when i was very in the beginning of my relationship with Hekate. I must I never truly understood/felt any connection to it neither.
The image is here if you want to look at it:
http://violaserpeverde.deviantart.com/gallery/25674747#/d1qwipwNow, the Keys, instead... i have silver miniature Keys on my altar, right beside Her portrait as TorchBearer and a small dog statue and a miniature snake i made myself. This seems to make my image of Her complete.
Don't get me started on the Crone thing. Something inside my mind rejects it even before seriously consider it. I feel a certain disdain toward the image in itself, whether it comes from me or Her.
On the general issue, i'm rarely satisfied with other people pictures/statuaries of deities i feel close to. I tend to prefer photoshoping gods myself until i am at complete ease with the result.