That is a very nice collection. I like the variety, and the level of detail explaining each different item.
Since about 22 billion of them were printed and it was around for 5 years, that stamp has a lot of opportunities for getting many nice and different types of cancellations, color shades, and other varieties.
My rabbit hole is plate number singles. There were about 2000 plate numbers for this stamp and I am about 10% complete in getting at least one of each plate number, mostly used. I realize I will not complete this impossible task in my lifetime, but it is still fun to see how far I can get. If that isn't enough of a challenge, you can try to get one of every plate number from each position in the sheet. I only have a few of those.

Have fun filling in the blanks and expanding on your new collection.
p.s. for future reference and easier searches, could you edit your post's title to include the Scott #319 in the title of the thread? That will make it easier for people to know what the thread is about before clicking on it.