Using a shell model which is capable of describing the spectra of upper g9/2-shell nuclei close to the N=Z line, we study the structure of two isomeric states 7+ and 21+ in the odd-odd N=Z nucleus 94Ag. It is found that both isomeric states exhibit a large collectivity. The 7+ state is oblately deformed, and is suggested to be a shape isomer in nature. The 21+ state becomes isomeric because of level inversion of the 19+ and 21+ states due to core excitations across the N=Z=50 shell gap. Calculation of spectroscopic quadrupole moment indicates clearly an enhancement in these states due to the core excitations. However, the present shell model calculation that produces the 19+-21+ level inversion cannot accept the large-deformation picture of Mukha et al. [Nature (London) 439, 298 (2006)].