We show that the fields of surface plasmon polaritons (SPPs)—excited by infrared ultrafast laser light—can be highly concentrated at the corners of thin, micron-scale gold triangular platelets. We present multi-photon photoemission electron microscopy (nP-PEEM) images and finite element method (FEM) simulations that show that the magnitude of the SPP electric field can be adjusted over a large range via control of the polarization, wavelength, and angle of incidence of the applied laser light. As it is well known that the strength of SPP near-fields has a strong bearing on non-linear photoelectron emission rates, localized SPP fields might effectively be used as a nano-scale adjustable electron source.