For my new website, orangeicons.com, I decided to design a promo wallpaper, in brand orange color. Here is how. Create new document, fill the first layer with solid orange color, and apply Gradient in layer effects (blend mode = overlay). Or, simply use Gradient tool to fill the layer.
Create new layer (Ctrl-Shift-N), then, important!, open Paths tool window, and create new path. Use Pen tool (P) to create a curve similar to shown here.
Switch to Brush tool (B), choose a brush with small radius (2-3 pixels), and in Paths tool window, click Stroke button (2nd in bottom row). If the line is not wide enough, click Stroke again. Then, remove the path, we will not need it any more.
Hit Ctrl-J to duplicate this layer. Then again. And then...
..make another 50 copies of this layer! Use Move tool to move last layer to the other side of the image.
link all layers with curves (to do that, click Link icon for all layers). Be careful not to link background layer!
Switch to Move tool (V), and on top bar, click Distribute horizontal centers" and "Distribute vertical centers". All curves should become equally distributed along the image and should produce nice geometric texture. HINT: the original curve was very simple
Merge all linked layers into one (Ctrl-E).
Duplicate this layer and rotate it 90 degrees. Now we have a nice curved grid!
Select background layer, then select pen tool (P) (but this time, do not manually create new path!) Once again, sketch a simple curve. it will automatically be placed in new layer. change its blend mode to soft light or overlay.
Similarly, use Shape tool (U) to add a couple of circles to the background. I added 2 circles with blend mode = soft light, and another white circle with blend mode=normal. I also applied very light gradient to this white circle, to give it pseudo 3D look.
The final touch is to add shadow to the white circle. Duplicate circle layer (Ctrl-J), change its color to light grey, choose Path Selection Tool (A), click to select circle shape, and use buttons on top bar to change its mode to "Substract from shape area". Then, group layer with previous (Ctrl-G). That's all! The only thing left is orangeicons logotype. but how I created it is the subject for another tutorial :-)