What can I put on Commons?

<img src="http://samwilson.id.au/wp-content/uploads/2013/09/log.jpg" alt="A strange log, completely devoured by worms. One wonders how it go where it is." class="aligncenter" style="width:100%" />

I never quite know what to upload to Wikimedia Commons. They say it accepts files that provide knowledge and are instructional or informative, but that seems so broad. Can I, for example, upload the photo above? It’s just a log that I thought was interesting because it’s so worm-eaten, and so neatly cut at each end (and the further end has two S-shaped steel hooks embedded in it), but it it within the scope of Commons? I’ve no idea. I suspect that it’s not, because it’s not a very good photo and it’s not of interest to anyone other than me. I could upload it, and it might stay there for a while, but surely someone will come along at some point — perhaps years down the track, when I’m no longer interested in it — and do away with it?

So I figure I’m better off uploading it here, where it can stay and be safely ignored by the world. I do just wonder, though, whether much the same line of reasoning can be used for very many photos that might be suitable for Commons. Actually, I don’t wonder it: I do not upload much there because I think what I’ve got to offer really does mostly fall into the same category as this log photo.

So I’ll stick to my own wiki, for now. Plenty of work for me on Wikisource, anyway…