Of course my natural reaction was: I do graphics, I can do it myself! But I can't paint the walls myself, I have no experience with painting at such large size for the wall (and my experience with painting is very little, watercolors on paper, back from elementary school), so maybe a better option would be to design the stickers with Inkscape, find a place to print them and use that.
But the time was short and I had no idea where to print large-size wall stickers (plastic), so ultimately I gave-up, bought something offline (in the Chinese market they have some decent ones, low price, pretty enough and from a quality point of view, they will last enough for the price).
Of course my creative self was not happy with the defeat, now I found some free time and designed one of the many ideas I had back then: a set of stars with the moon, all of them with funny faces. I won't use them as stickers, all I can do is to make them available as clipart, if anyone has some need for them.
About the other ideas... we'll see if I get the time and mood to put them down too (less likely, this set was the easiest).