How Do I Make a Better Map?

Okay, I started making a top-down game based on the ghost-shooter tutorial. Things are going well, but I'm worried about the size of my game now.

The basic concept is to make a background that isn't simply a single repeated tile. At the moment, I have a 2000x2000 pixel image that serves as my background, and I've used about 20 sprites or so to create walls for my character to collide with and enemies to climb over.

This serves fine for demonstration purposes, and people are enjoying the game- they just want more of a map to explore.

My first thought was to set up "Edge of the Map" sprites, so when the hero runs over them, the layout disappears, and a new one appears in its place, with the hero standing in the appropriate place. In other words, Zelda 1 Style.

This is where my problems occur. I don't want to bog down my loading or my game with 20 2000x2000px maps... I'd rather just use 15 100x100 pixel images and make some tile maps.

I did this once in Visual Basic 6... I made a subroutine that would read a text file and create the map I wanted accordingly on Form Load. (Layout start, here.) For example-

W,W,W,W

W,G,G,W

W,G,G,W

W,W,W,W

These four lines of text would be translated into a 4x4 grid that would have 4 Grass tiles surrounded by 12 Wall tiles. But in everything I've read, I don't know if Construct2 even has this capability.

THUSLY...

1. Would 20 large background images (like 2000x2000 pixels) be too much for a game I hope to use on mobile devices?

2. If that's a bad idea, then what about the text file approach? Using only 15 small images sounds like it would save a lot of space, but does the technology support it? I'm not after random maps here, I'm after a 20x20 grid that has a purposeful arrangement.

3. Is there a better way? Something I'm totally missing? I'm not married to any particular method. I just can't accept having one small image tiled a thousand times without any variety.

I know this is an incredibly long post, and I thank anyhow who reads it. I doubly thank any who reply, even if it's only to tell me that my post is too long.

Avatar Test!

In order to fade away the layer, you'd do something like:

System > On layout start > Black Screen > Set Opacity to 100

                           System > Wait .5sec

                           Black Screen > Opacity 80

                           System > Wait .5sec

                           Black Screen > Opacity 60

etc.

So basically, every half second, you'd be lowering the opacity of the object until it reaches zero. At that rate, the screen will transition from black to invisible in about 3 seconds.

If the transition is too blocky or takes too much time, try something like lowering the opacity by 5 every .1 seconds. This would change you from black to clear in about two seconds, with a fairly smooth transition.

Or you could play around with fade. I haven't found a fade button yet, so...