The corner squares on a tallit were originally intended to reinforce the garment and keep the tzitzit strings from tearing the fabric.  They have increasingly also become another design element. 

single star

double star

Gelfand

GrubmanF

Knoller

Kogen

Laff

Mendel A 

Miller 

Nelson 

Richman 1

Richman 2

Richman 3

Richman 4

Rosenfield 

Schulman (1)

Schulman 

Simon 

Werwa doves