All of mine 'game files' for ePSxe are thrown in one folder with mala's rom extensions showing 'bin, iso, img' (with no quotes) - other than that I dunno -
if you mean command line arguments, ePSxe_en.txt in the Docs folder of 1.70 shows:
3.5. Command line options.
epsxe [options] [psx-exe]
(*) -lib : Loads the libps.exe, which is necessary for running several demos. You should have the file libps.exe in ePSXe's root directory.
(*) -nocd : Disables the CD-Rom emulation. ( not recommended ! ;-) )
(*) -sound/nosound : Enable/Disable sound.
(*) -xasound/-noxasound : Enable/Disable XA sound.
(*) -audiocd/noaudiocd : Enable/Disable CDDA audio.
(*) -forcespu/-noforcespu : Enable/Disable SPU irq always ON.
(*) -cdtiming/-nocdtiming : Enable/Disable CDR accurate timing. (Gran turismo 2, Legend of Legaia, Dragon Valor, Point Blank series ...)
(*) -forcepad/-noforcepad : Enable/Disable SIO irq always ON. (F4)
(*) -memcard/-nomemcard : Enable/Disable memcard emulation. (Track & Field)
(*) -mdec/-nomdec : Enable/Disable MDEC emulation.
(*) -mdectiming/-nomdectiming : Enable/Disable MDEC accurate timing.
(*) -adjusttiming : Enable on the fly re-adjust timing.
(*) -oldtiming : Uses pre-1.5.1 timing.
(*) -fastboot/slowboot : Fast/Slow boot cdrom (psx logo).
(*) -nogui : Disable internal GUI.
(*) -ppf/-nppf : Enable/Disable ppf patches.
(*) -loadppf <file> : Load ppf file.
(*) -loadiso <file> : Loads iso file (CloneCD/Cdrwin).
(*) -loadcheat <file> : Loads a internal cheat file.
(*) -loadmemc0 <file> : Map file to memcard 0.
(*) -loadmemc1 <file> : Map file to memcard 1.
(*) -ssv0 : Save sstates version v.0 (1.4.0 or less compatible)
(*) -mouseN : Enable mouse emulation. (number of port)
(*) -analogN : Enable analog pad emulation (number of pad)
[psx-exe] : PSX-EXE, normal, zipped or .PLL with all files included in a .zip