Very pretty! About adding character... You can "cheat" a bit. You can add animal if it is easier for you although jams are for challenge (or at least for fun)
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In the center and in the top I see a shadow for those skewed blocks. I am not sure that the shadow should differ by size from usual blocks but it seems to me that maybe should at least a little? idk ¯\_(ツ)_/¯