Based on your post, it is likely that you already know these things... nevertheless:
1) The biggest thing is to remember that anything more than a double-stop must be rolled since a player is limited to playing two notes at a time with the bow.
2) If you are after realism, make sure that the combination is one that the player can actually finger. This is particularly a concern with triple and quadruple stops.
3) Again for realism, make sure that you allow enough time between chords, if played in sucession, to simulate the time it would take for a player to finger the next chord. This isn't really an issue with double stops, particularly on violin, but could be a factor with triple and quadruple stops.
4) Also, double stops and chords are more common in solo playing than in orchestral playing where the different notes are generally subdivided.