The cover shows us the new TIE Dagger.
On page 6 of the Art of The Force Awakens
we see a piece called ‘Falcon Escape’ by Ryan Church. This features TIE fighters with triangle shaped solar panels very similar to the TIE Dagger from The Rise of Skywalker
On page 59 there is another image of this concept from the rear that shows they were considering using “ocular turret rotation” for this this fighter. The caption by ILM Concept Artist James Clyne reads “There was talk at one point of a four-person TIE fighter, called the ‘quad-fighter.
‘ I had this idea of this ocular gunner in the back, evoking some of the World War II and Vietnam-era aircraft, which also had ball gunners on the back
The final version of the TIE Dagger appears to have a more traditional shaped TIE cockpit which leads me to believe it will be a single-man craft and not the four-man ‘quad-fighter’ version from The Force Awakens
The feature image on the Visual Dictionary cover shows one of the Knights of Ren.
Page 212 and 223 of Art of The Force Awakens shows some designs for the Knights of Ren by Glyn Dillon. One of which is almost exactly the Knight that appears on the book cover.
Its possible these costumes were made for the force back scene in The Force Awakens and reused in The Rise of Skywalker.
We’ll have to wait to get a better view of the rest of the Knights of Ren to see the other designs have been used and any other unused concepts from The Force Awakens.