Sourcefinding

Finding sources in the Undertale Image Collection mini-guide
(* as the stand-in for name/id in these)

From Filename:
	most sites don't have filenaming schemas that let you do this but here are the ones that do
	ex: "67818156_p0" pixiv filename, the numbers before the "_" are the post ID. enter the ID into the url "pixiv.net/en/artworks/*"

	ex: "TKP0915-1144244420058812417-20190627_100143-img1" image from twitter but not actually twitter's format, but a particular tool i use to save an archive of every image a person posted on twitter (https://github.com/furyutei/twMediaDownloader very useful on twitters with a lot of posts)
	"TKP0915" is the twitter handle, "1144244420058812417" is the status number (can be used to find the exact tweet), and last is just the date when the tweet was made
	twitter handle into twitter.com/*
	exact tweet can be found with "twitter.com/*/status/(status number)"

From Artist Name:
	names in the folder beginning with @ are always twitter handles
		for twitter simply use "twitter.com/*"

	otherwise i didn't make too useful of naming schema for the folders and you'll have to go by checking filenames to figure out which website they're active on
		if filename begins with tumblr_, than obviously tumblr, use the artist name in "*.tumblr.com"

		if filename begins with img_ and a long string, than it is from lofter and use name in "*.lofter.com"

		ex: "go_away_you_already_had_a_slice_by_smurfsass_ddm3qjn" is deviantart, use name in "*.deviantart" or "deviantart.com/*"

		ex: "58004217_440216206728433_7587781956151452851_n" is from instagram, use name in "instagram.com/*"

Source hunting sites:
https://saucenao.com/ and Google reverse image searching are the only two in my experience that are any reliable but if you're desperate:
http://iqdb.org/
https://tineye.com/
https://yandex.com/images/ (click the camera right of the search bar)