Clipping masks:
Make a new layer and make a shape (can be anything). Then make that layer invisible, and make a new layer. Apply image on that layer (ctrl + shift + alt + e, or image > apply image) and then make that a clipping mask (ctrl + alt + g, or layer > create clipping mask).
Then move the top layer around until you find a nice outcome and tadaa

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Brushes:
http://www.deviantart.com/Type in the type of brush you want (e.g. Splatter brushes, grunge brushes, cloud brushes, vector brushes, etc. etc.) and download them, then find the brushes folder. It will be something like this: C:/program files/Adobe/presets/brushes
Then drag the brushes into there and relaunch photoshop. Then go into the brush tool and right-click on the canvas to bring up a window. In the top right of the window there will be a little arrow - click that and it will bring up a drop-down menu. Select the brush pack you downloaded from the list, and then brush away

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Wireframes:
Type "Download wireframe c4ds" into Google, and then find some nice ones. Download them, and then ctrl + o (open) them in photoshop. It will open into a new document. Go into the move tool (v) and drag the layer into your other document, then set that layer to whichever one of these looks best: Lighten/Screen/Darken/Multiply
Cheers