Riot has visually updated most of the older champions in League, and a few of the remaining ones are planned for an update: Poppy, Taric, and Warwick (eventually, at least). But champions like Jax, Fiddlesticks, Nunu, etc. still have very outdated models and I haven't seen any mention of them even having a VU planned.
I mean just look at [this ](http://vignette2.wikia.nocookie.net/leagueoflegends/images/c/ce/Jax_Render.png/revision/20150129200734) vs [this](http://img2.wikia.nocookie.net/__cb20150607011805/leagueoflegends/images/c/cf/Jax_New_Dawn_concept_2.jpg). Obviously the second one is from a cinematic, but in the first one he looks like a short and fat little dude, not a fearsome warrior. Also, the new Jax skin would look so much better on a new model since the Warden armor makes him look even fatter.
Here are [Nunu's](http://i.imgur.com/D1kiqH6.png) and [Fiddle's](http://i.imgur.com/6XdxFNm.png) current models as well. There are definitely more that could use an update, I just felt like these were the ones most in need.