I second this motion.

I dont think its a good idea to start admiting minoritary file types, just think that most people who come here looking for art want everything as simple and straigforward as possible (reason why untextured models for example never get much attention), but if they provide that file type along with a more popular one its fine. Because seriously, I, for example wont download a totally unknown program just because i like one art piece thats made on it. I would look for other art that would fit the place and move on (unless its something truly amazing, which is quite rare)

Ideally, provide a .png and additionally an .ora inside of a .zip (is there built-in compression?).

If .ora is not compressed, this might be the only reason to reject it as a direct upload, but for now, please feel free to upload .ora inside of a .zip or .7z but for ease of use, I recommend you provide a .png as well.

I thought I'd replied to this already, but I guess I didn't. :)

While I support the idea of the .ora filetype, there are a couple things preventing me from allowing it directly:

1. Ease of use (this is the big one).  I need to be confident that a typical person will be able to make use of a file that they download from OGA.  At this point, .ora isn't a particularly well known format (it's the first I've heard of it, for instance).  If someone sees a piece of art that they like and downloads an .ora file, most likely they're going to have trouble opening it, which will leave them with a bad impression of the site.  I'm okay with people incuding .ora files in ZIP archives, but I want to discourage people from submitting only .ora files without uploading some files that are a bit easier to recognize along with it.  Unfortunately, the fact that it's an open format doesn't automatically make it easy to use.
2. Previews.  Ugh, I hate working with previews.  Previews are really touchy.  There are too many different kinds of images and archives and sound files that all have to be processed in different ways.  Any time I make any sort of change to them, they break.  Supporting an esoteric filetype for previews is next to impossible without doing a lot of code, and I don't have time to go there at the moment.  Once I add .ora to the list of allowable file types, people will want previews of it to work as well.

Note that these things aren't necessarily permanent.  If the .ora file format gets to the point where it's more well known and widely supported, I'll add it in.  For now, though, I'm going to hold off on this one..