how to modify the categories block?

[kwal_sky]

This is my ever first post here, so hi there everyone
I need modyficate an categories block, and don know, how to gets works...
For now, itd like a categories tree, when i click (or mouse over) on parent category, then subcategories show down...
I'll need get something like these:
In the block i'll only need show subcategories, witchout any trees of them etc, just in row. Also I need the links looks like:

. Every subcategory will have an picture.
Anyone can help me with this one?

Thanks in advice,
Regards.