I am not sure if this is what you are thinking about but with my Canon iPF5000 it has a layout check box for 'no spaces at top or bottom (conserve paper)'
This allows you to make a page size much longer than needed, batch all of your photo's at the leading edge then when you print it will cut the sheet just after the trailing edge of the last image. So, you make a custom size sheet like 24" x 50", if you only fill the first 20" it will cut it off there.
I do not know if Epson or HP have a similar check box.
Tony