You can choose from one of the preset filters (graphics file, office files, movies, etc) by clicking on the 'Select' button, or you can type in your own. Multiple filters are separated by a semicolon (;). You can create custom lists of file extensions to save for later use, and can combine them by selecting multiple lines from the list.
You can also choose to exclude certain file extensions should you wish.
Additionally, folder names can be excluded from the scan.
You can set the file size range of the search (Minimum and Maximum). You can also set the units for this value (Bytes, KB, MB, GB or TB). If 'Any Size' is selected then all file sizes are scanned.