>>1
If I understood what you meant correctly, then you'll lose how it looks. Compressed files (RAR, ZIP, 7Z) will always be assigned an icon by Windows based on the user's configuration (and the same icon for every kind). To customize them, you'd need two additional files - an icon (.ICO) and a shortcut (.LNK) pointing to the archive and setting the icon.
You could have a custom icon in a single file if you do the following - but step 4 will require some skill:
1. Make an icon
2. Make a RAR archive
3. Convert the RAR archive into an SFX (self-extracting) EXE file (using RAR/WinRAR too)
4. Edit the EXE file's resources with a Windows resource editor (Google) and replace its icon by your icon.
Only EXE files may have custom icons within them in Windows.