Photonic crystals are man-made crystals consisting of two or more kinds of different dielectric materials arrayed periodically. Because of the collective modulation of the periodic dielectric distribution to the incident electromagnetic waves, the directions of the group velocity and the phase velocity can be opposite, a photonic crystal slab can work as a negative refractive-index material. In the letter we study the influence of the dielectric shape on the negative refraction and near-field imaging of the photonic crystal slab. By the analysis of near-field imaging properties of the two-dimensional square-lattice photonic crystals consisting of circular, square, triangular, elliptical and rectangular rods, respectively, we find that the image spot moves laterally with respective to the rectangular slab when the symmetry of the rods reduces for a certain degree. With the systemic analysis of the equifrequency-surface contours, we find that an excellent-quality near-field image of the photonic crystal slab can be formed mainly by the self-collimation and the negative-refraction effects.