If the iPhone 15 Ultra is more than just a rumor, we'd be pretty happy for it to look like this concept from artist Jonas "PhoneDesigner" Daehnert, which he made with inspiration from the design of the Apple Watch Ultra.
As such, this render isn't based on any specific leaks. Should we get an Ultra iPhone in the near future, it may not look like this, as convincing as Daehnert's design is.
Starting on the back of the phone, the big change from the current iPhone 14 Pro is that the camera lenses sit flush with the rest of the camera bump. This makes the phone thicker overall (12mm/0.47 inches according to Daehnert), but makes for a sleeker-looking design.
The sides, rumored to be made of titanium on the real thing, have gone back to the curved shape of the iPhone 11 and older iPhones. The side and volume buttons stand out from the curved edge on flattened platforms, similar to how the Apple Watch Ultra's buttons do. Also, the alert slider, currently an oblong switch that clicks to the left or right of the side rail, is swapped for a textured circular switch that moves up and down the rail instead.
Also along the edges of the phone we see orange highlights for the SIM tray and around the (likely USB-C) charging port, seemingly inspired by the orange Action Button on the Apple Watch Ultra. It feels unlikely any future iPhone will draw focus to the SIM tray though, given that all iPhone 14 models sold in the U.S. only work with eSIMs, and we expect Apple to start eliminating physical SIM support for iPhones worldwide in the coming years too.
The front isn't the focus of this new design, but we can still see Daehnert's using a Dynamic Island like the iPhone 14 Pro. One change is that the display protrudes from the main curved sides of the phone, which looks good but doesn't seem comfortable to wrap your hand around for typing.
The first iPhone Ultra may not actually arrive until next year with the iPhone 16 series, meaning that this year's iPhone 15 Pro Max, while potentially different from the iPhone 15 Pro in more ways than just size, will still look like a familiar pro iPhone model. We're keeping track of all the iPhone 15 rumors though, so if there are any big design changes rumored for this year's models, we'll be sure to report on them.