Step 1: Create New File
Step 2: Make a New Layer & Plasma
Then, make some plasma on the new layer. Click filters -> Render -> Clouds -> Plasma.... and mess around with the "New Seed" button until you get a picture with much variation in it.
Next, you have to get the plasma another color. Press Layer -> Colors -> Colorize... and mess around with that until you get a nice picture.
Step 3: Make a New Layer & Plasma (again)
When this looks too dark, click on the dark layer and press Layer -> Colors -> Brightness-Contrast... to make it lighter.
Step 4: Qbist
Then, set the opacity of the Qbist layer to 15 or 25%, depends on what you like the most.
When you think this is too dark, again use Brightness-Contrast to make it some lighter.
Step 5: Text
Make a new layer, and make some text on it with the text botton in the main screen (it's the T button):
You can move it into the proper position with the move button:
Step 6: Rotation
Select your text and press the rotate button:
Then mess around with that buttons and press OK it will now look like this
Step 7: Merging and Scattering
Then merge the Background layers the same way so the layer dialog looks like this:
OK, select the background in the layer dialog and press Filters -> Noise -> Scatter HSV... and only move the value button until it looks nice:
Step 8: Bump Mapping
Then press Filters -> Map -> Bump Map.... and select the text layer (see picture)
And then only mess with the Elevation and Depth buttons until it looks cool:
Step 9: Colored Text
Select the text layer and press: Filters -> Colors -> Color to Alpha... and set the color to black.
Then merge the text layer and the new plasma layer:
Select the new layer and press color to alpha again, only now select the color white:
You can move the text layer a bit so it will look nicer, but that's optional. Last, merge all your layers to 1 layer. (when you don't do this, GIMP will ask for it when you save so you don't need to do this.)
After that, your banner is ready!
When you want rain on your text, also view my rain tutorial! https://www.instructables.com/id/ECISUY8JV9EXCFMB8X/