So, it seems that my memory was a little off. :-)
My mum found a piece of the fabric she and my dad used to make my little sleeping bag, and it turns out it wasn't exactly the way I thought: it didn't have any trees but balloons.
But it did have the light blue tones I remembered, and there were indeed clouds around... I wasn't too wrong after all!
And can you see the little flower at the top right corner? I really don't remember there being flowers at all...
I hope this little sleeping bag is still somewhere at home, and that we'll find it one day. I'd love to look at it again and try and remember looking at all the details years and years ago, when I was just a few years old.