1.i open particleillusionSE.
2.i Add a background.(layer0)
3.i want a 2 layer in the same time.
4.When i want have it say remove or replace the first background.
i can`t have two picture in the same time?(two picture mix togeter?)
you could make a sequence in that starts with one background and cuts/dissolves/transitions into the second one at the appropriate time. then export that as a quicktime, or whatever, then import that into PI as a bg and there you go.