your design folder take only one Imageand first open as photoshop and Alt + F9 and create a new action>Record, now it depends on design( Use Crop Tool shortcut key C and top bar, make width 500px and your design size) or use (ctrl+alt+I (Image size) width as 500pixels your chooses), in action panel >stop playing/rocecding.. After this you close the file and don't save it.
Then go to file>scripts>Image processor>select folder to process>select save location>File type, quality 5 or 3 your choose>Preference,Run action>set1>you action name>RUN.
One More Option Here :-
Go to file>scripts>Load Layers>Browse>Select all design>Ok,
After it will open and now crop it shortcut C and top two bar like arrow right and left there you go type 500 and 500 and Enter, then you ctrl+alt+I (Image size) width as 500pixels x 500pixels > ok
After Select all Layer shortcut key Enter, then you ctrl+alt+A, then File>Export>Expor layer to file>Browse Where you want to save>Your setting>Run