A historic design present in various cultures and traced back to Mesopotamia that was used extensively in European heraldry, with strong religious connotation and famously adopted as the symbol of French monarchy.
It depicts a stylised flower made up of three distinct petals, commonly held to represent a lily, though historical debate (and a quick visual comparison) would suggest it depicts an Iris. Present in design and print, its religious, royal and nationalistic connotations have kept it a popular motif in all arts and crafts and especially in home furnishings, on wallpapers and fabrics or as a background for traditional or formal design.
It’s likely that the constant popularity of Fleur de lys in furnishings has more to do with simplicity than royalty – the fact that as a motif it is relatively easy to copy, it can easily and effectively be up-scaled or down-scaled, drawn, traced, stencilled and embroidered.