Most of the information that can be gathered from these leaked screenshots are visual changes involving the creeps and the environment, but there are also two new heroes being played. Part of the early focus for HoN 3.0 on the test client seems to be implementing these aesthetic changes, as well as the ongoing testing of new heroes.
Two new heroes show up among the hero portraits. Purple's hero looks like some sort of green, masked figure, while Pink's hero appears to be a red canine. (It's possible that these heroes might not necessarily be part of the HoN 3.0 patch.)
Purple's chat appears in some of the screenshots, revealing that the name of his hero is "Dreadknight." We can also barely make out the top half of Dreadknight's model standing in the fountain.
The temporary spell icons being used for Pink's hero can be identified as Twin Head Dragon's Dual Breath (DotA) and the Druid's Dash, Mangle, and Nurturing Instinct (World of Warcraft).
Catapults look a lot different in these screenshots, and the Legion and Hellbourne creeps are distinctly colored in blue-green and red.
The Legion's fountain has been transformed into a cliffside tower structure, while the Hellbourne's has been connected to some stone architecture with a bridge.
Trees look more detailed on both sides of the map.
BUT
They are very rough early versions of things. A lot will change, a lot will be reworked, redone, and who knows where it will end up. Giant "WORK IN PROGRESS" signs need to be carried by the creeps. Heck they still use the old creeps death animations/effects and sounds, some of them are already getting redone, and just generally first iteration version stuff.
So keep that in mind. WIP, will change, enjoy your first look at what we are working on.
EDIT: Yes there are new heroes there. Deal with it, you get no information on them for now.” - [S2] Idejder
[S2] Maliken and [S2] Idejder were quick to point out that HoN 3.0 is being developed further than the version that is out on the test client. It's good to know that these changes are just the start. Much of the community is expecting that Patch 3.0 will bring a lot more than just visual improvements, and, hopefully, that's the case.
Links
imgur.com - Source
forums.heroesofnewerth.com - Source
forums.heroesofnewerth.com - Source