I could have told you without looking that Will Mallia made the map for 7 Days A Skeptic, and as Will is a regular here, I was sure he'd respond to this topic before I managed to post this. (And I was right! - shows you how long it sometimes takes me to write a post...)
While it's true for screenshot maps that the majority of the graphics used are not the mapmakers' own, there is still a lot of work in assembling them. Giving proper credit acknowledges the time and effort involved in capturing and arranging dozens or even thousands of screenshots, and/or employing hacking methods. (Maybe not the most exact metaphor, but people could praise your snowman or sand castle even when you yourself didn't make the snow or the sand - though I'm debating whether or not the comparison of the original graphics to snowflakes or grains of sand is appropriate or not... Anyway...)
In general, taking a small piece from a screenshot map is going to be just as okay as taking a screenshot from the game itself. That is to say, no one should mind if it's for some sort of illustrative purpose, such as a thumbnail or a small preview pic if in a wiki or blog you want to link to VGMaps.com, for instance. If you're going to show larger chunks of it or host the whole image, it is good practice to contact the creator of the map before doing so. If in doubt, it's better to ask than to not ask.
When linking to the images on VGMaps.com, please link to the bookmark on the "atlas pages" themselves, and not directly to the map images. In this particular example, you should link here:
https://www.vgmaps.com/Atlas/PC/index.htm#7DaysASkepticSomeone once told me it's proper "netiquette" (and who uses that term anymore?) to tell others when you link to their site; personally, I don't think that's necessary for everyone to tell me when they link to VGMaps.com, but all I ask is that you link like so and not to "hotlink". And then if the creator of the map actually allows you to host their map on your site, that's fine too, though it's still at least polite to mention VGMaps.com if that is indeed where you originally saw it.
Hope that helps.