Are you trying to add the pic through the common method - click the Insert Image icon, choose Browse, find your image, click open, choose size, click Insert Image? I believe if you are using the app, you do not see the icon bar, so it might be worthwhile trying through the Classic Site.

Apparently this is a common problem, though I have never had it happen to me. Sometimes it seems to be a browser problem - are you using Firefox?(which apparently can again sometimes be a problem though I just did one OK using Firefox)

Maybe the file is too big?

You'll have to open it in Paint and minimise the pixels.

I've had a bit of a look on the net.

Maybe the water jug is a separate thing if it's too big.

Maybe the set had a sugar bowl?

I'll keep looking