It's easier than it looks. Once you get use to the GIMP Controls it does most the work.
Like the first one. Step 1: white background. Step 2: Gradient brush with Gradient set to Flare Radial 101 and shape set to linear. Step 3: a few random strokes with the gradient brush. Step 4: I used the gradient but set the Gradient to Flare glow one and shape linear. Step 5: one or two more random strokes. Step 6: I think I did Filters > Enhance > Unsharp Mask which changed the color to the way they are now. (I was just goofing around with the differnt effects and liked the way that one came out. Step 7: text layer that says 200 Step 8: I did a filters > Alpha to Logo > Neon on the text Step 9: I removed the black background the neon put in and the "neon glow" layer and kept the "neon tubes" layer. Step 10: I think I did filters > Alpha to Logo > Glossy on the Neon tubes Step 11: I did Colors> Color Balance > Adjusted color sliders to give the numbers color again Step 12: filters > Light and Shadow > Gradient flare in the background.
It was something like that. The nature one was more me doing some free hand than just using GIMP filters and brushes. But for the most part it just took me awhile because I didn't really know what direction I wnated to take it and I had to fool around with the different effects because I'm not that familiar with GIMP.