Media Sizes
The Media Sizes dialog shows all the standard media sizes which are defined by default in the StoreFront system in the left panel. You can move standard sizes to the supported sizes to make them available for all media types. You can also create your own media sizes.
Assign Media Sizes 
1 On the menu bar, choose Advanced > Media and then choose Media Sizes.
2 Move the sizes that you want to make available from the Standard Media Sizes panel on the left to the Supported Media Sizes panel on the right by clicking the arrow in the middle.
The size is added automatically to the correct category. The category is created in the Supported Media Sizes column if it’s new.
3 Repeat to create a list of frequently used sizes
NOTE: Product templates can be created with custom sizes not mentioned in this list.
Add Custom Media Sizes 
You cannot add custom media sizes to the system categories so you may need to create a custom category first.
1 On the menu bar, choose Advanced > Media and then choose Media Sizes.
2 In the Standard media Sizes column, click the Add New Category button and enter a new Media Category Name.
3 Click Save to add the category to the list.
4 Click in the new category and then click the Add New Size button and enter a new size.
5 Click Save to add the custom media size to the list.
doc. version 6.0.4