>> I can share some of the places that I've found that look interesting to photograph with you and maybe you could give me some feedback. Since I don't know if they're accessible in winter or without a car:
-Swiss National Park: From the small research that I've done, it seem that I have to go to Zernez to get to this park. I don't know what in particular I would photograph here, but since it's a national park, I'm assuming its pretty.
I don't know most of these places from personal experience, so the info below is just what I have found on the web. Hopefully others will supplement this with their personal experience.
The Swiss National Park is accessible by bus, but closed in winter. However, note that you aren't allowed to leave the marked paths.
www.nationalpark.ch/en /visit/hiking/protecti on-regulations/
>> -Trift Bridge: I really like suspension bridges like this, but I'm not sure if it's accessible in the winter.
The season for the Trift Bridge is June to October.
Here are some other suspension bridges. You could check if any of them are open in winter
>> -5 Lake Hike in Pizol - A fellow photographer did this hike in the summer and all the lakes look gorgeous. I tried contacting the Pizol tourism website to check if it accessible during winter, or if the lakes are frozen by then, but I never got a response.
Here are panorama maps of the area in winter and summer. It's a ski area in winter. I don't know at what stage the lakes would freeze over and blend into the snowscape.
www.pizol.com/media/pd f/Infomaterial/Prospek t_Winter_16-17_klein_300x240_wwww. pdf
www.pizol.com/media/pd f/resort_info/Pano_Piz ol_Sommer_2016_mit-Logos_www.pdf
>> -Matterhorn view from Riffelsee: From what I've seen, I have to get to Zermatt, which is kinda far from the other locations I've looked at. Is it worth going all the way to Zermatt to check out Mattergorn and the city? The car-less town looks very pretty but I don't know if it's worth going all the way down there, or if it's even open by the time I get there.
Zermatt is lovely in the winter. It seems you can walk (on packed snow) to the Riffelsee in winter. It lies at a high altitude though, so I imagine it would freeze over at some point.
>> -Oeschinensee Lake: From what I've seen, the lake looks amazing and it has a small hike to a small restaurant/hostel kinda place.
The lake is frozen in winter, and you can walk on it
Again, I don't know at what point the lake would freeze over. Possibly not until January or February.
>> -Mount Pilatus Overlook: I've been looking for a good location to see the mountains, and this is one place that I found. Not sure if it's the best place or if it's accessible.
The cogwheel railway won't be operating, but you can get there by cable car in December
You need a clear day of course, and they will shut the cable car down if the wind is too strong, so you would need to spend a few days in Luzern/Lucerne to be sure of getting a suitable day to go up.
There are lots of other vantage points around Luzern as well as other places:
www.myswissalps.com/ac tivities/naturalsites/ mountains
>> -Partnunsee Lake: Another secluded lake with a small hike to reach it. Not sure if it accessible since it looks like it's in the middle of nowhere.
The season for the Partnunsee is June to October - another high-altitude lake at 1869m.
According to the site below, you can get to the start of the walk by public transport ("Öffentliche Verkehrsmittel"): Rhätischen Bahn train to Schiers or Küblis and Postauto bus to St. Antönien. (Timetable number 90.214 or 90.222). But not suitable for winter.
So it seems December is not a good time for most of the sites you have identified - except for Zermatt and the vantage points around Luzern such as Pilatus. As already mentioned, the other thing is that you need clear weather at high altitudes, which can't be guaranteed at any time of the year. That means you really need to spend a few days in each location to increase your chances of views unobscured by clouds.
Hope this helps to clarify some of your options!