This kind of art style is normally seen on smaller devises such a phones.
- 1-bit monochrome
- 8-bit grayscale
- 8-bit color
- 15- or 16-bit color (high color)
- 24-bit color (true color)
- 30-, 36-, or 48-bit color (deep color)
concept art- is when a artist creates an illustration that represents a game, and what they would like to see in a game, this can be anything from charters, assets, vehicles
concept art can be used for ideas for films,comics,games,animations or comics,
concept art can be a little scribe to a master piece of art work, also it can be used for additional ideaa to add to the work
http://fightingstreet.com/folders/artworkfolder/artworkpages/sf_art_pages/sfiv_art_pages/sfiv_pc_concept_art/sfiv_pc_concept_art.html 
httpswww.bungie.netenCommunitysort=2
texture art-in games is the illusion that the object or asset has a physical texture like wood
or metal,this will give a game a realistic feel when playing
it can also be used when CGI is used in the film industry t create something that is not there.
http://www.gamer.no/artikler/anmeldelse-anmeldelse-bulletstorm/138639
background graphics- these are images or a stage that sets an environment for the players and characters but these stages don't interact with players movement.
print media art
print media graphics- print media graphics is when games make merchandise such as posters, t-shirts or any type of clothing.
https://s-media-cache ak0.pinimg.com/236x/c5/d0/aa/c5d0aae7713174a4a00d890abce4a4c7.jpg
https://www.gamerabilia.co.uk/destiny-merchandise-memorabilia
https://www.gamerabilia.co.uk/halo-merchandise-memorabilia