I agree with Cypher. It's a lovely cage but there are safety risks for a small hamster like a winter white.
It looks like the Mayfair Gerbillarium which is about 40cm tall. With that height of cage for a dwarf hamster you ideally need a full level. But as Cypher says you can get round this by having the higher shelf lower and having the substrate up to the top of the glass. Maybe to within a cm of the top of the glass - and yes some may end up falling out - alternatively you could stick some cardboard or perspex inside the bars for about 2" just above the base and have the substrate to the top and then it won't fall out. May look a bit funny bit it'll be safer.
Hamsters are ground dwellers really and do better with more floor space and less height. They will climb bars and can even monkey bar across the top looking for a way out but they don't see well and tend to just let go and drop -if they fall from a height more than 25 to 30 cm and land on something hard (eg the edge of a shelf or one of the wood sticks at the bottom, they can break bones or die from injury or internal bleeding.
So when looking at the safety aspect you have to think of the worst case scenario, which is the hamster getting to the top and dropping, falling through the gap between the shelves and landing on something hard on the bottom. If you have nice deep substrate and nothing hard to land on (hard items can go under shelves) it cushions their fall. But there is still a risk they can hit the edge of a shelf and bounce off on the way down.
To get round all of this there's a need to reduce the height - either by making the shelves into a full level or having substrate as deep as it will go, or a bit of both.
The other thing they can land on is the wood ladders. So really the set up needs tweaking. Off to have another look at your photo to make some suggestions
