What practical uses can random hash collisions be put to?
If it is for completely random data you could still make a program that uses the random looking input to make different choices. For instance, you could sign two .jar files in Java, using the SHA-256 hash over the file in the META-INF folder. Then you can use the different files a property to make one choice or the other. Basically you're replacing one of the data blocks in a hash tree or list (which is in turn signed for Java).

Of course, most hash collisions don't work like that. For instance, the MD5 collisions need to be pre-calculated, but they work for normal data + a postfix. Even then, the amount of attacks that can be launched is limited. Faking a signature is such a big attack that the rest is more or less inconsequential.