You can go to Administration -> Settings -> Advanced -> ContentView -> Controls -> AlbumsBackend -> Views -> AlbumsBackendInsert -> Sections -> RootLibrarySection-> Fields -> NewSize -> ChoicesConfig - and there are the choices you can edit, update and add new sizes.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items