One which despite the lack of space encounters would be famous enough to justify inclusion in that wall display, but not actually an Enterprise?
Space is big. Just because we didn’t see the actual ship on screen doesn’t mean there weren’t tons of them out there doing cool things. We only saw the actual Ambassador class four times on screen, but that doesn’t mean there were only four Ambassador class ships in existence.
As noted, I can see this as an artwork honoring breakthroughs that led to ships named Enterprise (which would also explain why the TOS original was included and not its final state in 2285), but the concept-art idea happens to match the real-world making-of, which as we all know involved interpolating the Ambassador’s lines between the known Excelsior- and Galaxy-class designs. It need not mean that the Enterprise-D was practically finished as a ship design, only that a warp-appropriate shape had been calculated in the 2280s, and the sculptures’ inclusion in the conference room would’ve been a testament to Starfleet’s vision and the ability to execute it despite a misstep.
Sorry, I’m still not buying that the Galaxy class was a design Starfleet came up with in the 2280’s. It’s much easier to stomach that those sculptures were created specifically as 2360’s wall art depicting other Starfleet vessel classes, with the aircraft carrier thrown in as a tribute to the Enterprise-D specifically.