ffmpeg script encoding only few inputs
You have to feed all inputs to the concat filter, and set the correct number of inputs in n. FFmpeg input index starts from 0. So the fifth input has an index of 4 and would be fed as [4] in the concat filter.

ffmpeg -i body.mp3 
    -framerate 60 -loop 1 -t 16.368 -i frames/000000.PNG 
    -i 1.mp4
    -framerate 60 -loop 1 -t 3.959 -i frames/100100.PNG 
    -i 2.mp4
    -framerate 60 -loop 1 -t 6.574 -i frames/200100.PNG 
    -i 3.mp4
    -framerate 60 -loop 1 -t 5.134 -i frames/300100.PNG 
    -i 4.mp4
    -framerate 60 -loop 1 -t 4.559 -i frames/400100.PNG 
    -i 5.mp4
    -framerate 60 -loop 1 -t 5.351 -i frames/500100.PNG 
    -i 6.mp4
    -framerate 60 -loop 1 -t 4.390 -i frames/600100.PNG 
    -i 7.mp4
    -framerate 60 -loop 1 -t 8.950 -i frames/700100.PNG 
-filter_complex "[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]concat=n=15:v=1:a=0[v]" 
-map "[v]" -map 0:a -pix_fmt yuv420p out.mp4