Use
ffmpeg -i input.mp4 -i %04d.png -i another_input.png -filter_complex "\
[0]drawtext=text='Text to write':fontsize=180:fontcolor=white:x=500:y=800:enable='eq(n\,25)'[tmp];\
[2:v]scale=20:20[ovrl];\
[tmp][ovrl]overlay=860:500:enable='eq(n\,0)'[tmp1];\
[tmp1][1:v]overlay=0:0" output.mp4