How do I specify multiple file extensions for images?

On the Field Options dialog provide a list of valid image file extensions, separated by a semi colon:

Specify a list of file extensions separated by a semi-colon

EasyCatalog will attempt to import images using the list of file extensions in the order given in the list, so if you would prefer Photoshop images to be imported instead of JPEGs ensure that the .psd file extension appears first in the list.