So, two things. The first is that frequently, when I try to search for a picture to add using Pixabay, nothing happens after clicking search. Since Pixabay has a habit of hanging randomly, I'm never sure if nothing is happening because of a lack of matching search results, or if it's because it's hanging again. There should be a message displayed when there are no matching search results.
Another thing I noticed is that Pixabay often returns results that do not match the exact search term, which doesn't happen when searching with Google. As examples, searching ターキー with Pixabay returns results including images of waterfalls (たき), and searching 蓋/ふた returns results including images of pigs (ぶた); when searching these same terms using Google, the results are pictures of turkey legs for the first term, and lids/eyelids for the second. If would be great to be able to get only results matching the term searched (normally putting quote marks around the search term would do this, but although it changes the results when searching with Google, it does nothing when searching with Pixabay).
I've seen the first happen before, will try to track it down.
I will take a look at the data returned from pixabay, but I'm not sure I'll be able to do any additional filtering on top of the results they send back. Naturally, google is going to have a better "idea" of what you are looking for.
1. The engine is meant to say "no results" if none are found, but there are (thanks to you prompting me to look at the issue) apparently two ways to report that, and I was using the less reliable of the two. It should report correctly in all cases now.
2. Unfortunately, this fuzzy searching is done on pixabay's side, and there is no way to disable it. On top of that, I will post below what a result from pixabay lookjs like. It shows the original English tags, so a search done in Japanese cannot be accurate filtered on renshuu's side because there is no Japanese to filter on.