Yes, but Bosmer already had three/three-and-a-half zones in the base game, same with Breton and Nord. And Bosmer especially seem unpopular, with their furnishing styles being some of the worst selling ingame. The only Imperial zone we have is the Gold Coast, and even that takes a backseat to the Dark Brotherhood story rather than that of the Empire. That's as if the only Redguard zone was Hew's Bane focusing on the Thieves' Guild, but no they already had Alik'r, Stos M'kai and most of Craglorn.I'll agree regarding furnishings, but Imperial has had a number of costumes already (three male, four female, Pelinal's Robe). There's also the Order of the Hour motif, plus a zone DLC and a limited-time home in addition to the three base game homes.
There are also the gladiator style stuff which seems to be Imperial in style to me. As well as the Midyear Mayhem crowns and the one you can earn from an achievement.
Meanwhile, Bosmer hasn't had anything new in terms of DLC or new homes. Nord hasn't had any zone DLC, though there have been a couple of dungeons, plus Hakvild's. I don't count the Snow Globe since that is, technically, Imperial in style, just stuck in Eastmarch. Breton hasn't seen any proper DLC either, or new houses.
There are chunks of Skyrim not in the game yet, as well as chunks of other regions.
Imperial isn't the only race/culture that could use more content.