The subject of combining images to create great backgrounds is what we will cover here. This is a beginner tutorial so I will not get too indepth on this topic. For demo purposes, I will combinefour images into one background then place a bike in the new background. Here are the images:
Layer 1 - Orange Sunset
Right click and save this image
Layer 2 - Blue Palm Trees
Right click and save this image
Layer 3 - Eagle Head
Download this .psd file
http://uploadpsd.com/file/19123.psd
Layer 4 - HD Logo
Download this .psd file
http://uploadpsd.com/file/19131.psd
You would open Layer 1 and duplicate layer by dragging background layer to the "New Layer" Icon at bottom of the layer palette. Delete the original background image by dragging to the trash can at the bottom of the layer palette. This will leave you with an editable layer which we will call the final image.
Now open the Layer 2 image and drag contents to the final image. Now you have two layers. Set the opacity of layer 1 to 83% on the layer palette. On Layer 2, change the layer mode to Luminosity @ 100% opacity. Image should look like this, pretty kewl huh...
Open up Layer 3 - Eagle image (19123.psd) and eagle layer to the final image. You should have three layers now. The eagle needs to be reversed so let's make sure that the eagle layer is active in the final image and then click "EDIT / TRANSFORM / FLIP HORIZONTAL". Select the "MOVE" tool and move image to the far right side. Set layer mode to (Linear Burn @ 69%) in the layer palette. Now your image should look like this:
Open Layer 4 - HD Logo .psd and drag contents to the final image. Move logo to the top left corner and set the opacity to 49% in the layer palette. Congratulations, you now have a decent looking background to insert a chopped bike. Here is what your image would look like with the bike inserted.
This is the completed .psd
http://uploadpsd.com/file/19124.psdso that you can see the layers if you are having a problem getting your's to work. Try to follow the steps above so that you will know how to manipulate each layer and make the necessary changes to acheive the desired result.
When you understand the basic layer theory then you can use it to adjust the final image any way that you want it. For example, I would screen the HD logo into the background, apply an overlay layer over the bike layer to warm up the bike colors and blend with the surroundings better. I would also plant the bike better by building a surface for it to sit on and adding a shadow for a more realistic effect. Here is the direction that I would head.
Hope you have a little better understanding of the basics of layer use now. Have a great day!