Here's a quick Photoshop trick to create a symmetrical background. This is another interesting technique to create an ordinary background to something more interesting. Below is the 2-minute short video and a summary steps from the video.
1.) Use the Rectangular Marque Tool (M) and make a selection. 2.) With the Marque selected, copy the selection to a new layer Command+J (Ctrl+J). 3.) Transform the new layer Command+T (Ctrl +T). 4.) While in Transform mode, flip the new layer (Edit > Transform > Flip Horizontal). 5.) Drag the new layer to mirror the original and press "Enter" to accept the changes. 6.) Use the Crop Tool (C) to expand the visible area if needed. 7.) Use the "Patch Tool" to clone out any visible stitching. After making a selection, Edit > Fill, drop down "Content-Aware".