Presuming you mean an app that can change icon associations en masse from predefined/saveable sets, not just one-by-one, as you can do with -for example- Nirsoft's FileTypesMan, try...
PortableFileAssociator
http://portableapps.com/node/15583
This was developed for temporarily changing file associations (associated apps and icons) from a USB stick and reverting all changes at the end of the session.
But you can use it to change icon associations only, from sets defined in editable text files, and bypass the reversion at the end of the session (i.e. make the changes permanent not temporary). You can still undo the changes by running the app again.
One catch: the file "Type" descriptions of changed types gets prefixed with "PFA", even if you only change the icon association, but there may be a way round this.
This one has the advantage of being (I think) the preferred choice at PortableApps.com, with reasonably active development and forum.
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Similarly...
Assox
https://sites.google.com/site/assoxhome/
I haven't tried this one, but it looks very comprehensive (from scanning the somewhat overwhelming manual).
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If you're still on XP, you can also try...
Icon Phile
http://www.freeware-guide.com/OldGoodFr ... Phile.html
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And related: for changing application icons on Win7, on the taskbar and app. titlebar, etc.
7CONIFIER
http://www.addictivetips.com/windows-ti ... 7conifier/
I haven't tested this one but others have.
http://wronex.deviantart.com/art/7CONIFIER-177688442
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None of these have the ease-of-use or versatility of XYplorer's CFIs

, so I would still try out icon sets there before making system-wide changes to the registry.