You are correct, how to get them here... I have wondered since long. Thought that PC users would all be "Yeay, tons of assets" but unfortunately not really. Then I thought I should start uploading content, as the users that primarely wanted to blow off the asset database by uploading days and night did not do so (lack of interest, dunno), so I started to search for stuffs I could import to create a basic in hop to interest people. So I did start extracting stuffs from others on PS and shared about 80 assets, including those you mention, doobiesnax icons he kindly proposed on PS forum to share but couldn't as an xbox user.
I think the key is content, a growing database of asset and fresh stuffs to discover. Social media was a good point and I have added already quite a few people that might add SparkShare in return. Any newly shared asset will generate a twit that will be seen by many. To grow, I think we have to share and promote what we share, interest people with things they can't get easily. Once the ball rolls, I think it will grow...
Now, about how things work... Thing is, I have spent a huge time on SS, and I'm glad I did it, really enjoyed doing it. I'm just saying that the state it is now is for me sufficient to prove worthy or not. I have tons of other ideas I could implement, such as my always wanted dev blog for creators, or an instant "kodeshare" on SparkShare, with brain auto generation... But I'm holding these until I see that there could be a real interest from a potential community.
About how everything works internally, well it's not that hard. The search function will return anything that has something to do with your search request. It will search in assets names, author names, pack names, descriptions, presentation and will return that in the form of tiles split into categories. The main idea is to present the first page with 4 latest asset and a tile leading to the rest of the latest assets. Of course, if the base gets gigantic, the catalog will be messy, but the whole concept/key, is the search field. Because in the head of a user, I'd go on SparkShare with a precise idea of what I need, and I'd search for it most likely.
I have implemented packs in a way that makes them not unique, so that you could share an "icon" pack and I could as well, without them being the same. But searching for "icon" would bring them both up in the results. I personnaly did not share anything yet, but I am sharing with a "SparkShare" account stuffs I do extract from existing games in PS, so I do not personally get the download credits and all. In a past version, from almost the begining, I had "categories" almost implemented, but after long discussions with some from the alpha/beta participant, we decided to remove them in favor of newly born idea, the "packs" idea. Now, you cannot share your content under SparkShare packs and I don't really think that would be needed, as it would narrow down the possibilities in the end.
All can be discussed of course, I'm totally open to ideas. Great changes at this point wil ltake more time as I will not reboot the entire base, but can still occure