Paintings?

[Seraphor]

Having just done the EW vistas myself, yes you need to discover every single vista in a 'set', and each expansion is it's own set.
This of course requires completing the jump puzzle of each expansion, so if you want ANY paintings from Stormblood zones, you need to get to the top of Kugane, jump off, and land on that lamp post.
Luckily the Radz-At-Han one isn't so bad.

Or you can buy them off the marketboard. The strange thing is though, if you search for 'Paintings' it only displays the first 100 results with no options to change page, so you'll only have paintings from ARR and a bit of HW on there. You'll need to search for individual painting titles to find anything after that.
There aren't too many available though because not many people unlock and/or sell them, and those that are tend to be listed for wild prices of anything between 10k and 100k.

[Jojoya]

Having just done the EW vistas myself, yes you need to discover every single vista in a 'set', and each expansion is it's own set.
This of course requires completing the jump puzzle of each expansion, so if you want ANY paintings from Stormblood zones, you need to get to the top of Kugane, jump off, and land on that lamp post.
Luckily the Radz-At-Han one isn't so bad.

Or you can buy them off the marketboard. The strange thing is though, if you search for 'Paintings' it only displays the first 100 results with no options to change page, so you'll only have paintings from ARR and a bit of HW on there. You'll need to search for individual painting titles to find anything after that.
There aren't too many available though because not many people unlock and/or sell them, and those that are tend to be listed for wild prices of anything between 10k and 100k.

Are you typing in the word "painting"? Key word search on the MB is always limited to the first 100 results.

The better way to search for Paintings is to go down the Housing section and clicking on the Paintings subcategory. I'm able to browse all 315 paintings that way. Preview is an option there, just like it is at the Joyous Painter, but you don't need to have discovered the vista to preview.

The problem with trying to sell the paintings on the MB is that it's hard to predict what players will want to buy outside of a handful of popular ones and they tend to sell slowly. Those listing slots are usually better used to sell items that will be bought same day or next day. If we had a much higher limit on the number of items that could be sold at one time, we'd see a greater variety in the listings.

That's what I suggest asking a friend with the all the vistas unlocked. A friend will generally be happy to buy it for you in exchange for the actual vendor price.