I am making a 2D top-down game in Java using the Slick2D library. However, this question applies to all ways of making games of this nature.
My question is: How would I do a background for the world. Currently it looks like this:
Obviously, this isn't the best example, as the right side has an area that allows the player to walk into the 'background'. However, I am asking how this is done in other games, such as Pokemon.
If you're working on a plain style map, you can either stop the map from scrolling and make the player move "beyond" the center of the screen OR stop the map from scrolling BEFORE you've reached your limit minus half your screen size.
If you don't want to use the method Byte56 linked, another option is to just make a bigger map. You don't have to put transition points right at the edge of the background. If you can see up to 20 tiles away, ensure that the "playable area" of the map is within a 20 tile border of the map. Note that this can be a bit jarring/annoying to players if you don't somehow make it very visually clear where the transition point.
Games like Neverwinter Nights (2002 version) would automatically extend a tiled map out but shade out the extended area. Thus a pathway that led right up to the "edge" of a map wouldn't just end in darkness but would visually appear to stretch out into the fog. The darkened shader along with NWN uses a clickable highlight region for transition areas made it clear and obvious where these transitions were but also make the map edges look less like an entire map was inside a box and instead part of an expansive, endless world.
There's also approach Heroes of Might and Magic chose - they render a border around the map and fill the abyss with stone texture:
