1. Me neither. I personally prefer a skin named "Clean". I think you can easily swap graphics on that fw by Stereophonick with UniversalSkinner. However you will need to find out its offsets first (these are the addresses, where image start is within the binary ezkernel.bin file).
For me it's simple enough to find new offsets if graphics is original. However in case of fw with modified graphics it is not that simple to do.
2. Yes for now it works, as long as you are talking about official
1.06_fw7 as well as any other firmware, offsets of which are known and injected in definitions.xml.
3. Boot screen depends on skin's colours which are represented by image named "ezkernel_Colors Map (until dialog is developed).png". This image consists of a column of 10 pixels of different colours. Some of those are responsible for the loading screen background and the text on it.
4. Technically, you could modify it yourself, as EZ Flash Omega fw is open source. However it is way easier, if you use a modified firmware with those functions and try to change its skin.