Linear Death Pack

not difficult... Background is composed of three files :
Background image
Background second image ( a sort of light)
And clouds.
Clouds, yes. Look at your game : you'll see clouds moving.
The two background images can't be edited. But the clouds can
It's menu_cloud_overlay.iwi in iw_03.iwd. Just modify it as you want, and save it as DX-T5 without mipmaps^^

The yellow lines don't look electrified. They are electricity^^

that's impossible for the moment, because the only way is to modify the cloud file, and doing that means :
-what you modify will be animated
-what you modify will pass under the original image

You'll have to wait for a tool to be made for this, if it come one day...
But you can just make the smoke like I said, though.

Well, i didn't modify the image file, but the cloud file...

What you want to do is to put your own image, fixed, instead of the actual soldier background.
It's totally different from what I did : by modifying the cloud file, I've put like, a texture, which is animated, and displayed twice under the actual soldiers file.
What you have to do is to modify menu_mp_image.iwi or something like that, but it's an image in ARGB format, so you won't be able to convert it back to iwi, whereas the menu_cloud_mp is in DX-T5 format, so that it's possible to convert it back to iwi...
So for the moment, the only part of the background which can be modified is the animated part, the menu_mp_cloud... So you can only put your texture in animated alpha and twice displayed mode, that would be awful for a background like yours, only patterns could be used... Sorry.

If you didn't understand, try to modify the cloud file with your texture and you'll see what happen.

I'm trying to tell you that the only thing you can do is modifying the clouds... you can't modify the picture because the dds has to be saved in ARGB format, and dds2iwi can't convert ARGB files...