Limit the disk space each user of your Gallery can use.
Quotas limit the amount of total disk space that is allowed to be used for images and other items. Gallery 2 can use two types of quotas: User quotas and group quotas.
These quotas are checked when a new item is added. If the item would cause the quota to be exceeded, the file will not be added and a message will be displayed to notify the user.
The option to add, edit, or remove a quota is available in "Quotas" after going to "Site Admin".
In Gallery 2.2 the module has a block to show the quota and disk usage for the current user. Add this block in theme settings.