How to Create Steampunk Photography Using GIMP

Beyond the Basics

1. 
   Start with the original photo. Sure, applying the sepia effect automatically was easy, but with manual control we can get something much better, so let's redo that step manually.
2. 
   Turn it into black and white (a quick way is to desaturate it - Colors > Desaturate, but you can also use convert to grayscale and then back to RGB).
3. 
   Select a light brown as foreground (painting) color, add a new layer, fill it with that light brown.

   1. Optionally rename the layer "sepia" to help you identify it.
      
4. 
   Add a Layer Mask to the brown layer and leave it white (full opacity).
5. 
   Now go to the background (photo) layer, select everything, go back to the sepia layer, select its mask and paste (paste into the mask, not into the image layer).
6. 
   Anchor the selection.

   1. The result will look funny, but do not get scared, it's ok.
      
7. 
   Just change the layer mode from "Normal" to "Color".

   1. And you will have a good looking sepia image.
      
8. Merge the layers.
9. 
   Add a border. Use the Fuzzy Border filter (Filters > Décor > Fuzzy Border).

   1. Take care to select a good color for it (use the color picker and take a sample from the picture) and a good size.
      
   2. And the result is something like this.
      
10. 
    If you want to defocus, add a little Gaussian Blur or if you want to go the opposite way, just sharpen it.
11. 
    You can also play with the Color Curves.