Here is the finished one.

Create some more shapes.

Step 19 : Back to Illustrator

We will create some more line work in Illustrator. Let's start by creating a couple of blend objects.

Colorize.

Paste into Photoshop.

One more blend.

Bring into the composition. Apply Color Overlay.

Here is the fun part. Put some little squares randomly and connect them.

Paste into Photoshop, apply Color Overlay.

Create yet another blend. Bring it into Photoshop, apply Color Overlay.

Create circular blend.

Bring as Smart Object.

Reduce Fill Opacity to zero. Apply Gradient Overlay. This hides the object partially.

Duplicate the object. Flip Horizontally and modify the Gradient.

Step 20 : Adding skyscraper

Open up the Skyscraper image. Apply Halftone Pattern filter to the image. Go to Filter > Sketch > Halftone Pattern. Press "D" key to reset the colors to default before you apply the filter.

Your image should look like this.

We need to select the black tones and separate them. Go to Select > Color Range. Make sure your background color is black. This will select all the blacks.

Press Ctrl+J to create new layer from the selection. This looks like pop art.

Drag & drop this layer into our main composition. Place it above the Characters group.

Double click on the layer icon. Adjust blend settings. This will blend the image based on the values of the underlying layer.

Step 21 : Background pattern

Create a new pattern that we will use to apply to the background. Create a new document and create square pattern. Turn off the background layer, marquee the area and go to Edit > Define Pattern.

Create a new layer and press Shift+F5. Choose the pattern you just created and press OK.

Place this layer just above the background layer.

Zero the Fill Opacity. Add Gradient Overlay to the layer. This gradient hides the center portion of the pattern and reveals at the edges which is what we need.

Step 22 : Adding texture

Drag & Drop the paper texture into the composition. This will add more character to the design. Resize it to cover entire canvas. Change the blending mode to Multiply. Reduce the opacity to 90%.

Adjust Curves to strengthen the texture a bit.