Hi
when you say modified what do you mean - what steps did you take?
when I was resizing - it was important to note that the image files need to be the coirrect size resolution for the display
see the nextion site for the actual resolution per display
and i also had to resize the area of the background image in the nextion editor to cover the whole display
if you do not resizze the display area then the image is fitted into a smaller area
this is independent of selecting a ddifferenty size device in the setup - as this only resizes the canvas - not the elements
Matt