The shape of IF4+ is square pyramidal.
To understand why, we can look at the molecular geometry based on the VSEPR (Valence Shell Electron Pair Repulsion) theory. IF4+ has a total of 6 regions of electron density around the central iodine atom. This includes 4 bonding pairs (the bonds to fluorine atoms) and 2 lone pairs of electrons.
With 4 bonding pairs and 2 lone pairs, the ideal geometry to minimize repulsion is octahedral; however, the presence of the lone pairs will cause a deviation from this shape. In an octahedral arrangement, if you remove two lone pairs, ideally opposite each other, you are left with a square pyramidal shape, where the 4 fluorine atoms occupy the corners of a square and the iodine atom sits above the plane formed by these atoms.
In summary, due to the configuration of its electrons, IF4+ exhibits a square pyramidal structure.