I had a pretty busy christmas:) Hope yours was great too!
If you use Folder Marker you can best place the icl files in it's icl folder. I have Folder Marker Home (found that out on checking LOL) and for me that folder is "C:\Program Files\Folder Marker\Icl\"
But there is one inconvenience when you chance the default icl's on Folder Marker --- it copies it's icl files to an Appdata folder and if you don't delete or replace the icl's there, you won't see any change.
For Folder Marker Home that folder is here: C:\Users\*username*\AppData\Roaming\ArcticLine\Folder Marker\Icl\
If you have trouble browsing to folders in C:\Windows etc. you can use Freecommander, which is a handy program to have anyways :)
If you want to use more icl's you can use the Folder Marker Folder for that - if they are foldericons.
But if you want to change file icons, they are pretty useless in Folder Marker and it tkaes time for Folder Marker to load them, so I'd place those else where.
I just created a folder in C:\Program Files called 'Icons' (hehe, original huh?) and I drop any icons I want to use in there. I don't even put these in icl's, but keep them as ico's, because when you want to change the icon on a shortcut that is the easiest to browse to ;)