Generally, vector artwork is best. That's genuine vector artwork not an image embedded into a vector file format. If that's not available, then a high res PNG or JPG is usually good enough. Because the majority of NFC tag print is quite small, then the resolution of artwork can often be quite low and still print OK.
However, for the best print, high resolution (200dpi or better) or vector (EPS, PDF, AI, SVG) is best.