Ibn Fadlan account describes their tattoos as reminding of pine trees and vines.

As an archeologist specialising in early Medieval Europe, I encoutered several artistic motiffs that crop most often among the Norse, Pomeranians and Northern Slavs.

That would be:

• svastikas,

• Thor's hammer,

• knotted rope, vines or bands,

• simplistic horses and even unicorns,

• runes,

• triqvers-triscelions (3 hooked svastikas),

• the solar wheel (a circle with a cross inside),

• [the hand of god] (http://bialczynski.files.wordpress.com/2009/07/swietesymbole9-rece-boga.jpg),

• a circle with a dot in the centre,

• interwined squares or triangles - VALKNUT, here, below the horse,

The same motiffs range from the Vendel Period to the post-christianisation of Scandinavia, and from Lapland to Normandy, and appear on pottery, leather, jewelery, weapons, tools, engravings, and virtually everywhere (the northmen had a thing for decoration apparently). While we do not have any evidence that the Northmen of Viking Era tattoed themselves, we have clues, namely:

• the proliferation of decorative motiffs on anything they owned.
• the popularity of religious tattoos among their neighbours, the Saami (Laplanders), with which they intermarried (this is well discussed in another thread on r/askhistorians)
• the fact that through out the ages, sailors were the main "carriers" of tattoos, and the Northmen of Viking Period were consumate sailors and travelers.

So in essence, we do not know if "Vikings" had tattoos, but the re are good clues that they did, and IF they did, that it was a combination of geometric motiffs, braided/knotted lines, floral motiffs, religious symbols, runes, and possibly animal motiffs (horses, dragons etc).

Source: Im an archeologist who excavated viking burial sites in Pomerania and Masovia.

EDIT: formatting.

The Norse actually didn't really have tattoos.

I assume that the "Arabic documentation" that you're referring to is the account of Ibn Fadlan in the 10th century. He apparently met with Rus traders who were "as tall as date trees", "combed their hair daily" and were covered, basically head to toe, in tree like patterns and other figures of dark green or blue/black.

Unfortunately a search of Norse/Viking tattoos always goes back to Ibn Fadlan's account, which leads me to believe that if the Norse people did practice tattooing, it was far from common.