The default catalog folder is the location where Express Server puts images that you upload to create a new catalog, along with other associated files. The LizardTech factory default location is C:\LizardTech\Express Server <version>\ImageServer\var\catalogs\, but you can specify a new default location for newly created catalog folders if you wish.
NOTE: When you upload imagery to create a new catalog, the location specified here will be what you see in that catalog's Catalog Folder field on its Basic properties tab unless and until a new location is specified there.
To specify the default catalog folder: