I think I would make a series of blocks, just squares and rectangles in various arrangements, and sized to fit with the size of the panel, then play around with the arrangements of the blocks. The piccie (pulled from Pinterest) shows a randon assortment of blocks.
Try the panel in the centre and try it on the thirds - a third of the way up/down and a third of the way from the left/right.
For colours; stick to what's in the panel but get as many different fabrics as you can.