I will be creating my Upcycle project to have the aesthetic of an antique wood postcard.
Guadalupe Mountains National Park Postcard 
This aesthetic uses vibrant colors, simple shapes, and figures to create complex scenes. This style uses a lot of colors to create a vibrant scene. These colors are muted to create a vintage look. This style is also common on antique travel posters.
Glacier National Park Postcard 
I will be creating my Upcycle Project in this style because I find this aesthetic very cozy and “homie”. I enjoy how this aesthetics are able to bring a lot of colors into a space. This style makes me think of cozying up to a fire with a cup of hot chocolate.
I will be making a light switch cover out of cardboard for my Upcycle project, so I hope to create this aesthetic by painting different pieces of the cover with muted, beautiful oranges, blues, and purples. I enjoy how the small additions of colors to the room to bring an eclectic style into any space.
References “Guadalupe Mountains National Park, WPA Style, Lantern Press Artwork, Wood Signs and Postcards.” Lantern Press, https://lanternpress.com/products/wood-signs-guadalupe-mountains-national-park-wpa-style-lantern-press-artwork.  Amazon.com : Glacier National Park, Montana, Bear and Spring Flowers … https://www.amazon.com/Glacier-National-Montana-Postcards-Stationary/dp/B097CKB22W.
This is a lovely topic for the upcycling project, and these classic “travel style” posters have a special place in my heart, as they brighten up any room in a very subtle way, making any space “cozy”, as you discussed. The colorful, simple scenery and the simplistic text prompts one to think of nature, and the beauty of our world. Do you have a particular location in mind, or are you copying the aesthetic for a general location? Either way, best of luck in creating this!