In the classroom, you are bound by the resolution of the projector.
Aim for images that are at least 1024 pixels wide.
If your image has greater dimensions than this recommendation, the projector will resample them into images that fit the standard of the projector, which is typically 1024 x 768 pixels.
Projectors in A&A classrooms are monitored for color accuracy and bulb strength. Even so, due to the respective native settings of projectors and personal devices, be aware that an image may appear differently projected in the classroom versus on your laptop screen (monitors are generally well ahead of projectors in terms of presenting detail). Likewise, digital images can appear very different in color due to the color settings of their monitors.