I have finally got round to creating a map of I2b. The frequencies being low in most of Europe I had to use a very fine scale, with gradient of 2% at a time. Sadly there isn't any extensive study of German and Swedish regions, so the extend of the two hotspots of I2b is far from accurate.
In Belgium, let's note that Wallonia has 7% of I2b, considerably more than the 4.5% in Flanders. It's strange since Flanders is supposed to be more Germanic, and the percentage of I1 doesn't vary much between the two regions (12% in Flanders and 11% in Wallonia).
There are many theories concerning the presence of I2b in Russia, Ukraine and Moldova.
1) They are remnants of Paleolithic hunter-gatherers.
2) I2b was part of the Indo-European haplogroups, and some pockets have survived around the Pontic-Caspian steppes.
3) The (Swedish) Vikings brought I2b to Russia, and the Ostrogoths to Moldova (Chernyakhov culture, which corresponds to the Gothic kingdom of Oium).
Personally I think that the third theory is the most likely. As for the I2b in around Greece, Albania, Bulgaria and northern Turkey, they must have been brought by the Visigoths at the end of the 4th century. The Visigoths would also explain I2b in Italy, south-east France and Iberia. Note that these regions all have a fairly proportional level of I1 too. Obviously the Suebi are responsible for the I1 and I2b (and R1b-U106 and R1a) in Galicia and Portugal, and the Normans for the same Germanic package in north-west Sicily.