Hi. First off, I moved your question to its own thread. It was in the "post picture to show off your themed iPad" thread and I didn't want it to get lost in the scrum. Plus, it was rather off topic...
Rather than me typing everything over, here's a link where I gave an overview of Shrink:
http://www.ipadforums.net/jailbreak-applications-tweaks/45241-shrink-change-size-icons-labels.html
Iconoclasm is a tweak that allows people to design springboard layouts. How it works, I have no idea, but there is a whole section in Cydia dedicated to it. With this, you can set up your springboard to have any style, practically, of icon layouts. You can have layouts of squares, diamonds, pages of of 10x10 icons (which is why Shrink will come in handy - so they fit), etc. think of it as Gridlock beefed up (as you can have more than the stock 4 x 5 grid.
As far as non-themed icons go, there are one of two things happening:
(1) Either there is no icon made for that particular theme, in which case you'd have to ask the developer to maybe make one, or
(2) There is one but the name of the folder, icon, file address, etc. has changed. To fix that, you'll have to dig into the theme and your iPad to see what the difference is so that you can fix them. it's not really hard, especially if you have iFile and/or something like iFunbox; it's just tedious.
Hope some of this helps/clarifies. Let us know how you get on.
Marilyn