ffmpeg: is it possible to have a text slideshow with a static image in background?
Use ASS or SRT subtitles. You can make them with Aegisub or manually in a text editor. Then use the subtitles filter:

ffmpeg -loop 1 -i image.foo -vf subtitles=your_subtitles_file.ass -t 60 output


You did not mention your desired output format so I made a very generic example.