It's a fantastic set up. And welcome Mrs C. Unfortunately the lid doesn't give enough ventilation. It would need to be all mesh apart from the wood surround, to give enough ventilation. Hamsters are very prone to respiratory infections and need very good ventilation. 1cm square mesh is quite easy to fix to a wood frame and a hardware store would cut it to the size you want.
- yes thought it might be a mesh/frame lid x
Or for cage ideas maybe? There's a thread called "Show us your cages" which has a number of ideas on.