List of files must be not an alias, but a text string.
Adding something like that to your code must help:
setPhotoshopFilestofilesoffolder_to_runasalias list
setFileNamesto {}
repeatwithifrom 1 tothecountofPhotoshopFiles
setcurrent_filetoitemiofPhotoshopFiles
copycurrent_fileastexttotheendofFileNames
endrepeat
tellapplication "Adobe Photoshop CS6"
activate
try
setBatch_Optionsto {class:batch options, destination:save and close, error file:Error_File, file naming:{document name lower, extension lower}, macintosh compatible:true, override open:false, override save:true, suppress open:true, suppressprofile:true, unix compatible:true, windows compatible:true}
batchscript_namefrom filesFileNamesfrom action_set_name with optionsBatch_Options
endtry
endtell