I think its important to note there is a definite difference between an environment artist and a level designer. There is a lot of confusion on the internet as to what defines each job role because the more complex game design has become the more designers/artists have been required to create a AAA standard title ready to be shipped within a timeframe, but there is a clear way to seperate these roles these days.
Level Designers (LD) create the actual gameplay and scripted events that are to happen within the levels - combining pacing with skill, ability and player knowledge to create exciting scenarios for players to play through. An Environment Artist (EA) will take an approved LD's level and 'art it up' using a combination of textures, 3D assets, particles, lighting and practically anything else that isn't gameplay specific or change the way the level is played.
There seems to be two workflows for an environment artist, one is that they go through a very basic level that has been constructed by an LD and use a variety of modular assets to craft around the blockmap. The second is to tailor make the scenery from the initial blockmaps, insuring that each section of the game is unique and handcrafted, this method has its drawbacks with additional textures and 3D models alongside longer artist/designer development time (having to create unique assets that are not reusable).
