I think your third shot had the most contrast, but other than the jewelry with the green gems, you captured a nice monochrome set of shots! You can try out playing with a lower f-stop and a faster shutter speed....or a higher f-stop and slower shutter speed to capture some low light details!
I'll give it a go. I photographed another item yesterday, wrote the post today...I'll post it probably Wednesday. Also low light but in colour.
I'll try those settings with something tomorrow though. Not sure what but I'll think of something.
I'm sure you will come up with something interesting! Looking forward to checking them out.