Use the following render flags in the render script box to override your render settings:
Replace imageformat with TIFF, TGA, BMP, IFF, JPG, PICT, PSD, RLA, RPF, B3D to override the Save Format stored in the project file.
Example: -oformat JPG
-oresolution width height
Replace width and height with the desired pixel resolution to override the render resolution stored in the project file.
Example: -oresolution 640 480
To select which take you need rendered . You can only submit one job per take. Also, you need to apply the quotation marks.
Example: -take "BackGround"
Don't use numbers or underscores in the take name.