A Smol Songbird

Hello Anon! I will try my best to answer specifically to arranging your characters for group pictures - if you mean individual posing it will require another answer ^^;

Staging: Best to do in sketch mode so you can go as messy as you want - if you have individual poses prepared, think of staging to rearrange the characters and play with position and scale. The original is the left side which seems to convey a family portrait - good for showing off personality of characters :D

Now simply by rearranging it gives a different feel! The right side seems to show a story - I assume Original Jakob is the hero/MC, Long-haired Jakob could be a villain or secondary MC, and everyone else are minor/supporting characters.

Shapes: Use big shapes to draw attention and make it visually cool! Idol picture uses the portrait staging as I place equal importance on each character and I want to show off their design. But the triangle gives an interesting layout compared to the boring Jakob portraits. Azura is front and center as the leader, and the supporting members surround her, arranged to sit in accordance to their personality. 

SMTxFE picture follows the story staging - this is an epic battle taking place (inspired by this btw :D). Scaling is used to convey the importance of characters (Chrom and Flynn as leads and fighting solo VS the others engaged in a skirmish), Circles form a natural loop and keep the artwork ‘contained’. While the human characters look outwards, the enemies ‘look back’ to keep the focal point towards the middle.