1. Find some art you like.
2. Click the title of the art to open the submission page for that art. (clicking on the "play" button for music or sound effects will allow you to listen to a preview of the audio, but you will have to click the title to open the submission page. See screenshot below)
3. Once on the submission page (for example, here) scroll down below the preview to where it says File(s): 
4. click the file link right below that.

No response from submitter. Unless the copyrighted vocal components can be removed, or the origins clarified, I will be removing this submission soon.

It sounds like the goal here is usability over completeness, which I applaud. As for what gets included or not, my opinion is:

• If any tiles are present in more than one collection/atlas/submission, and both collections/atlasses/submissions are to be included in this curated set, only one copy of each tile should be included, omitting all duplicates.
• Any two tiles that are very similar but have no material stylistic difference (just a color correction, or pixel cleanup, or a fix to an animation frame) then these should be treated as "duplicates" and the more "correct" or "improved" version should be included and omit the other.
• Stylistic disagreements should be evaluated to see if they "fit" and if having them improves the set or not. The LPC styleguide should be the, uh.. guide for what fits or not. But it is just a guide. If the people participating in this project feel this set is made better by a particular inclusion despite that tile not adhering to the styleguide, it should still be included. When in doubt, consult your fellow project participants ... then decide what you (specifically bluecarrot16) feel is best regardless of the opinion of your peers; you are the resident expert and the leadership that assures cohesion of it all. You get ultimate veto power. OGA accepts everything, even if the "LPC" tag isn't really appropriate. The advantage to this project is curation. DON'T accept everything. If it doesn't make it better, it shouldn't make it in.
• What "fits" or not can also operate as a spectrum or prioritized list, too. Incorporate the "classic" LPC components first, working your way to the more stylisticly divergent assets later. Given enough time, absolutely every LPC asset will be reviewed and incorporated (or not), but until that fantastical day arrives, the set will always have the most widely-used and widely-recognized stuff in it first.
• I think including non-tileset assets should be considered. If there is another curated collection that handles some part of the LPC stuff (like castelonia's character generator) then those don't need to be included, or at the very least they don't need to be included yet. That stuff can be added last (if ever) since an alternative solution is in place for those parts. UI, Inventory items, Portraits, Non-character animations, Visual effects, et cetera all just seem like one more category each alongside Terrain, Buildings, Indoor decorations, Outdoor natural features (or however the rest of the tiles end up being organized)
• .tsx files should be included. Perhaps not as an absolute requirement, but anywhere they can be added, they'll be helpful. They don't hurt the people that won't use Tiled, and they sound like the perfect way to provide invaluable organizational and contextual information.
• editable source files are... meh. blend modes and the like are cool in .psd and .xcf files, but not really used much in a tile atlas context. I think the most valuable feature of those files are image layers. Tiled files support layers, correct? I say the most universal source file is a lossless flat image format (.png). the Tiled filetypes handle everything else IMHO. If someone prefers GIMP or Photoshop over Tiled, the tiles would already be available as individual .png's that can be quickly imported together as a stack of layers. Both Photoshop and GIMP have a tendency to change their file format, so for instance, opening an older .psd file is not guaranteed to look the same depending on what version of Photoshop is opening it. To my surprise, Tiled seems far more feature-stable to me.

TL;DR: I'm excited about this! :)

Feel free to disregard anything I've suggested. My opinion as a non-artist should be taken with a very large grain of salt.

Thanks for making these available! Wonderful work.