Here are some suggestions for ways of setting out work on a display board. I find that ‘hanging from a line’ and ‘standing on a line’ are very useful. It’s important, I think not to distract the eye from the work.
If straight lines are being used it’s worth while making sure they really are straight. Nothing looks worse than work that’s mounted slightly ‘off’. I try to use an improvised plumb line (pencil tied to a bit of string) to make sure my vertical lines are spot on.