Well I really love the MetroUI in Windows 8 but is there any possibility to resize the tiles ?
You can make them half the width but I'll assume you'll actually mean more than that; so, you can also change how many rows of tiles you have, effectively resizing them to fit less or more on the screen.
regedit from the Start Screen (you can search for it), then navigate to:
Create or edit the DWORD(32-bit) value
Layout_MaximumRowCount and set it to a preferred value. Please note that there's yet another hardcoded limit such that you can't get more rows than your screen resolution allows to; so, for some screen resolutions you might be able to get another row if you're lucky but for others you'll only be able to decrease the amount of rows and not increase them.
There are also some other settings there, you might play around with
Layout_MaximumAvailableHeightCells to see whether they also affect resizing.
Old question but may help someone.
Windows 8.1 contains refinements generally received well, for some of the "rough edges" of Windows 8. (It's hard to bring in something new and get it perfect in version #1!).
The refinements in Windows 8.1 include New UI tile resizing and scaling (within limits) which may answer the question.