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i think it would be a great idea if plasma and the plasmoids were more transparent/blurry (like the OSX dock), also few nice high resolution wallpapers should be added

Transparency/blurriness is dependent on the plasma theme. You can change plasma themes by going into (KDE 4, not sure how they rearranged things in KDE 5) System settings -> Workspace Appearance -> Desktop Theme. There you can select between various themes installed as well as download more that people have submitted with a wide range of transparency settings.

For wallpapers, you can similarly choose between those already installed and a wide selection of user-submitted wallpapers, or provide one of your own.