Your wheel looks like the mini silent spinner wheel? The size up from this, the medium, (or 6.5" silent spinner" is an ideal size for a Chinese hamster.
The mini ones are really even too small for a roborovski.
Otherwise, your tank looks good. Ventilation is key and a lot depends on which substrate you use also. Carefresh will have less aroma than wood shavings for example inside an enclosed tank, so it`s being aware of any strong phenols or scents which may smell fine to us, but to a small animal who breathes these in at close proximity, it would be like us living in a room that smelled of lavender or pine all the time. It would soon drive us nuts, I`m sure! x