In reply to robnights:
It sounds very much like you're after walks rather than roped climbs? Something impressive looking but only borderline-technical in mountaineering terms? In that case I'd point you to the UKH Route cards:
https://www.ukhillwalking.com/logbook/r/find.php
There have been some good recommendations already so here's some more route-specific info:
Tarmachan Ridge: https://www.ukhillwalking.com/logbook/r/?i=81
Beinn a' Bheithir: https://www.ukhillwalking.com/logbook/r/?i=819 (the round described here includes an ascent of 'Schoolhouse Ridge', grade I... but also points to a non-graded alternative)
Bidean nam Bian, a big traverse: https://www.ukhillwalking.com/logbook/r/?i=100
Stob Ghabhar via the (other) Aonach Eagach ridge https://www.ukhillwalking.com/logbook/r/?i=83
Big skills-stretching winter walks through impressive terrain don't have to involve ridges of course. Here are a couple that you'd be likely to find challenging/worthwhile:
Creag Meagaidh: https://www.ukhillwalking.com/logbook/r/?i=936
Braeriach: https://www.ukhillwalking.com/logbook/r/?i=49
...to be honest it sounds from the tone of your post as if pretty much any winter Munro day would fit your needs. Apologies if I'm under-estimating the group's experience there.
If you did want to move up a notch from the borderline walking/mountaineering ridges to slightly more challenging grade I stuff then these would all be good places to start:
Coire Gaothach side of Ben Lui. The classic choice is a circuit of the two ridges enclosing the corrie (go up the left hand one, as it's steeper). This route card doesn't tackle the more scrambly ground but should give a good impression of the hill: https://www.ukhillwalking.com/logbook/r/?i=922
Traverse of Beinn Alligin: https://www.ukhillwalking.com/logbook/r/?i=591
CMD arete: https://www.ukhillwalking.com/logbook/r/?i=47
Ring of Steall: https://www.ukhillwalking.com/logbook/r/?i=930
Stob Ban and Mullach nan Coirean: https://www.ukhillwalking.com/logbook/r/?i=833
There are loads more days along those lines of course, but that should get you started...
And for some more inspiration/information, a few articles from the archives.
Winter ridges for walkers and mountaineers https://www.ukhillwalking.com/articles/destinations/winter_ridges_for_walke...
Grade I winter, 12 must-do routes: https://www.ukhillwalking.com/articles/destinations/grade_i_winter_12_must-...
Classic Winter, CMD arete: https://www.ukhillwalking.com/articles/destinations/classic_winter_-_ben_ne...
Winter walker to winter climber - here's how: https://www.ukhillwalking.com/articles/skills/series/winter/walker_to_climb...
10 serious mistakes winter walkers make: https://www.ukhillwalking.com/articles/skills/ten_serious_mistakes_winter_w...
Winter essentials for beginners pt1: https://www.ukhillwalking.com/articles/skills/series/winter/essentials_for_...
Winter essentials for beginners pt 2: https://www.ukhillwalking.com/articles/skills/series/winter/essentials_for_...
Winter essentials for beginners pt 3: https://www.ukhillwalking.com/articles/skills/series/winter/essentials_for_...