Having arbitrary sizes for icons / tiles I think is still required. I'd maybe go with a consistent gradient / no gradient approach.

Personally I'd go with no gradient and a flat colour.

While Google's lack of consistency in icon sizing is frustrating (though it is getting better, slowly), real world usage does look much better than that, as the icons are centred rather than placed on a baseline. http://i.imgur.com/CYUVTw8.png

That being said, I do think that rounded squares are an important part of iOS's design and that style icon is associated with iOS, so I don't think it should be changed.

They don't look anything like the messy image you posted at all.