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And done.

Per Scattrd below, hearts never spawn within 2 squares of each other
Also wall sections never appear in the corner.  I think the larger pattern is that they never appear with both pieces on the border.

And minor correction, Minotaurs and chests are adjacent to the left or right, but never above or below each other.

Another small pattern :  In addition to walls coming in pairs, I've never seen a wall piece in the corner.

Bottom option won't work as the 7s are quadrant constrained and can't be side by side. 

Anyone find a pattern or something special about the 2s or 3s?  I've found something for all the other numbers (including the 7s - hint look at the dot on the shield).