So Blood Angels have Talanted (Trade [Artisan]) what exactly Artisan can do(it's kind of a general description)?

Paint pretty pictures.

A little on skills and Talented talent. A skill must be trained to gain skill mastery, but a character can be talented in any skill regardless of training.

Obviously Trade (Artisan) is a Basic skill concerning making works of art and the recognition of good art, artists, or art styles. It falls under the General Space Marine Rank 1 Advance: Trade (any).

"Trade Skills allow the character to create things, from guns to starships (even artwork) . Characters with this Skill can earn money or reputation plying a trade. They can identify the works of particularly famous or infamous craftsmen, or recall information concerning items of their trade."

DW:C p.106 Italicised emphasis mine.

An example of this trade in use:

A Blood Angel techmarine takes up his kill-team brother's broken chainsword and rebuilds it. As Blood Angels prefer asthetic over bland industrial functionality he uses his Trade (Artisan) skill to work in some detailed engravings and filagree (in keeping with the original owner's chapter asthetic i.e. engravings of great wolves and not nude cherubs for a Space Wolf).

herichimo is exactly right in terms of skills and the talented feature.

However, an artisan is "a worker in a skilled trade, especially one that involves making things by hand." It has nothing necessarily to do with art itself, though that certainly applies. Someone who makes shoes, clothing, armour, watches, furniture, weapons, or buildings is just as readily an artisan as someone who paints or carves embellishments. In fact, as you kinda inferred from your initial question, it's a general term that would be applicable to any one of the items within the Trade skill group.

Now, here's where it gets tricky: The Trade (artisan) skill doesn't actually exist. The Trade skill group is an Advanced skill, not a basic one, which means that without taking that skill, the talented feature does not apply, as herichimo so aptly stated, but you can't actually take that skill because it doesn't exist as an option within that skill group, just as you couldn't take pilot (flying), as it's not an option, and is way too generic regardless.

However, that's not as big of a deal as you might think, because the trade skill itself doesn't actually do anything . It states that "characters with this skill can earn money or reputation plying a trade", but it doesn't provide any mechanics for how that happens, or what impact that has on the wargear available to characters, so based on the renown and requisition system in place, it provides exactly zilch benefit without GM fiat. It also states that "They can identify the works of particularly famous or infamous craftsmen, or recall information concerning items of their trade", but unless the GM is *really* going out of his way, that is unlikely to come up in any mission context, and is far, far less likely to be called upon even in the types of scenarios where it could be useful than say any of the lore skills.

So, a few recommendations: First and foremost, rather than house ruling in the creation of a rather ambiguous new skill to an already ambiguous skill group, I would replace it with trade (any), as artisan is a term that would apply to a follower of any of the skills within the trade skill group. Secondly, I would strongly recommend talking with your GM before taking *any* Trade skills. Work out with him exactly when it would be used and how, what kinds of tests would be made and what benefits would apply. It's one thing to say that your character has trade (armourer) and can "design, upgrade, and forge weaponry", it's quite another thing to figure out when (if at all) your character has the time and resources to *actually* forge weaponry, what effect that has on available wargear for missions, and what exactly "upgrading" that weaponry does.