That's a good question! What I've done was look at images of an aurora background and then took the right one. Then I used a lensflare as well which is how it's bright. I also added a line right there and used the glow feature and messed around with it to get it to have that strong glow.
I used the same image but I went into GIMP and I used the perspective tool to know that I wanna make the ground skewed since I couldn't do that correctly in Flash. Then I used the color changer to mess around with the floor by changing it's hue, contrast, brightness and all that. Got the background made which I visually loved!
As I put my character Salt in, I actually made a new Symbol and had 3 layers to where it's the Head, the Body, and the Tail. Then I took that Symbol and placed it on the background. I made another Layer then placed the same sprite and rotated it to go under her and then I used the ADD blend and some transparency to give it that visual floor look that has a reflection. Then I added some red glow to Salt just an extra detail.
For giving that Space look right there of Salt's sprite. I originally wanted to Mask it, but it ended up glitchy and I didn't feel like fixing it to where it worked specifically better. So I just made a cut out of the space background by just "Break Apart" of the bitmap (Not trace bitmapping). and then made 3 layers of that, tricking the system to where I can get a cutout of Salt that has the spacey texture. I took a full colored sprite itself and then placed it on the same layer of the broke apart space texture. Now that texture has a open spot of Salt. So I took that frame and place it on the next layer where there's no cut out and then I recolored it and it left the texture shaped as salt like that. I removed the outside pieces and then now I have that symbol and added some Glow to it.
There ya have it! Graphic Designing at it's finest. Especially in Macromedia Flash 8, too.
That's really amazing my friends,I plan to be a graphic designer as well.