Our team's art bible showcases all of the concept art created for our project. It is managed primarily by our teams two artists - Archie and Luke - and was made on Powerpoint.
I wasn't really involved in the creation of the art bible, but I did have input during early concepting over the style that our game will use (a mix of realism during the introduction segment followed by a more stylised battle and mirror dimension segment inspired by Stranger Things). Additionally, the decision to base the battle on a train comes from my game - which was entirely focused around using trains as a metaphor for the different stages in a person's life.
Luke worked primarily on developing concept art for the game's main character, while Archie worked on concept art and environmental art for the Conductor and Train respectively. Archie used Photoshop whereas Luke used Krita (out of preference and familiarity). The art bible is an important piece of documentation that showcases our game's visual style. It's not just limited to the environment and character design, and can include elements like UI art and colour schemes.
Our art bible ensures that designs remain consistent across the two of our artists (Luke and Archie) by providing one-another with visual examples for them to reference when drawing more concept art or creating 3D models / textures for game-ready assets. Additionally, there will be visual consistency amongst the environment and character designs with the use of colour palletes and common referencing mateiral.
If I were to do the art bible myself, I likely would've used Miro (which they did originally but swapped to Powerpoint) as it works more seamlessly for adding new content quickly, whereas with Powerpoint you have to add a new slide for each time you want to showcase a different piece of concept art. Additionally, our team has collectively agreed that artists should focus on the art bible while developers and designers (me and Ethan) should lean more towards helping out with the GDD.
In my opinion, I think our art bible is fairly effective at conveying the concept art in an organised way. Its main strength is that it's well organised, with character art, environmental art, and animation style all given their own segments on the document. However, the main issue I have with it is that it lacks UI art, which I could really use so I can make placeholders that more accurately reflect how the game's UI will look in gold standard.
I believe our art style (stylised to a degree, leaning towards realism in the first half of the game and more dark and stylised art style for the second half in the mirror dimension) is appropriate for our intended age range of 12+. Other RPGs of similar genres typically have a stylised but grounded art style as well, and are typically popular (on release) with the same age range.