There will be 2 other ressonance structures. One of them will have a pi bond connecting the carbon that had the positive charge and the nitrogen. The lone pair that was on nitrogen, has moved to form that pi bond. The second will have a pi bond connecting the same carbon and the oxygen. One of the lone pairs from oxygen will form that pi bond.
Work Step by Step
1. Draw the lone pairs. 2. Find which pattern does that structure fits. It is the second one, but a lone pair is next to a positive charge, so that lone pair can come from the oxygen or from the nitrogen. We will draw both cases. 3. Draw the arrows: Follow the pattern for a lone pair next to a positive charge. (The lone pair forms a pi bond to the positive atom.) 4. Do the changes based on the arrows. * Don't forget the formal charges!