That highly depends on what you want to achieve.
If your project is not going to be gfx-heavy I highly suggest to store the graphics in the cap.
If gfx-heavy and mostly sprites are used, I would store the images outside the cap and load them at runtime into the blank sprite images.
Animating a sprite while constantly loading the pictures from harddisk is bad, though, so you have to load them at once at app-start /layout start or change.
After all storing gfx externally leads to more flexibility, but you may stumble accross problems with e.g. image points coordinates in terms of setting them anew.