doubleohfive, the legacy walls included sailing ships and the NASA space shuttle (no Richard Branson VSS Enterprise either
). No "in-universe" reason to exclude it. I liked how they mentioned in Enterprise that Archer had planets named after him - and then I saw a TNG that ended with them setting course for one! Obviously a fluke, but still cool.
But each display was differerent. They incuded some ships named Enterprise but not all. There were multiple aircraft carriers with that name but only one is represented on the TMP and TNG walls. (and on the NX01 display) The Ring ship is ony in the TMP display. I think the Ent-E only has Federation starships in its display.