One has to unset the key binding for the action bound to the key before one can use the key for another action.
`->` (cursor-right) and `<-` (cursor-left) are bound to the action `next_img` and `prev_img` respectively.
So using:
# unsetting the keys bound to next/previous image by stating it without assigning any keys:
next_img
prev_img
# further unsetting:
zoom_in
zoom_out
scroll_right
scroll_left
scroll_up
scroll_down
# custom key mapping:
zoom_in plus
zoom_out minus
scroll_up Up j
scroll_down Down k
scroll_left Left h
scroll_right Right l
# assigning new keys for showing next/previous image
next_img space
prev_img BackSpace
makes feh use the arrow keys for scrolling and space/backspace for next/previous image.