Good day and welcome!
As the corresponding rejection says, those were rejected by the automatic process (ML/AI filter).
Your example for the playground sign may have been correctly rejected as a duplicate of Saint Monica Playground that already exists as a wayspot. The sign alone in this case would not necessarily be eligible by itself; but may act as a placemarker for an eligible object (the playground). The same logic may apply to the others as well as the “murals” that may not be seen as artistic murals following Unique Art.
I suggest posting the nominations for more precise advice for each. It may be best to post one first for a continuous topic discussion.