The areas outside of Ellensburg like Umtanum Ridge always feel different to me since they are basically high desert. Watch out for rattlers. https://www.wta.org/go-hiking/hikes/umtanum-ridge-crest

I’ve always wanted to check out more of the scablands created by the Missoula Flood but can’t tell you any specifics of good hikes in the area. Probably pretty easy to find something.

Not different biome, but have you done the Kendall Catwalk? Its a benchcut in solid rock a hundred feet up. Built by the WPA, I believe. https://northbendescapes.com/kendall-katwalk/ https://www.wta.org/go-hiking/hikes/kendall-katwalk

Ever tried snow shoeing? Definitely a different hiking style.