What visual artifacts should we expect from the images that will be released from the James Webb Space Telescope? Specifically, do we expect 3-pronged diffraction spikes (any preview how they would look?)? Do we expect any artifacts due to the honeycomb-like structure of the main mirror?
The image below (taken from that webpage) shows simulated point sources as they would appear on the detector (including the sampling by the 0.0656 arcsec pixels). The greyscale is on a logarithmic scale of brightness. Each postage stamp corresponds a 77x77 pixel region around the point source, imaged through filters at different wavelengths (identified by the code in the top left, where 090 corresponds to 0.9 $\mu$m etc. and the W or M corresponds to wide-band or medium-band).
Then there is a further web page that gives the equivalent information for Near Infrared Camera (NIRCam), which has a short-wavelength (SW) and long-wavelength (LW) channel, as well as several filters associated with each of these.
Are you asking about the PSF (point-spread function)?
There are some simulations & basic images available as well as a downloadable package you can use to compute the PSF for a particular instrument and wavelength. Since the telescope hasn't been fully assembled yet these are based on simulations.