Exactly. It's like @djennyfloro says. If we copy the link of the picture above, we can see this:

So, when we upload a picture in Steemit, it is saved in the servers of steemitimages.com, in files.steempeak.com or any other front-end. The Steem blockchain only saves that link to the image.

Yes, it is partly decentralized. When those servers fall down, your pictures disappear.