But if you change this with something like Opalescence (or are using the Faceless One), then your background commander would be affected and could be targeted by anything that says commander creature. Most of the cards that refer to commander creatures instead of just commanders are background cards themselves
Both of these have their own pros and cons
You want even, natural light on a plain, dark, non-reflective background and your own photos, and you definitely shouldnt use a stock image pulled from Google
If a card says loses all abilities (like Darksteel Mutation or Sudden Spoiling), that permanent still keeps any +1/+1 counters, loyalty counters, shield counters, or other counters already on it
Im not and have never been an MTG judge, but you can sit back and enjoy this summary of how to use the level up mechanic (insert Super Mushroom sound)
Ready-to-play 51-card deck