By default ProFTPd transfer all files in BINARY mode. This will work fine for images, zip files, other data files.
When you upload scripts, mainly .pl and .cgi (perl scripts), you have to upload then in ASCII mode to get it working.
Many FTP clients are smart enough to upload .pl and .cgi files in ASCII mode.
If you prefer, you can set ProFTPd to start all transefer in ASCII mode. This can be done by editing /etc/proftpd.conf
If you do this, make sure you upload all images and other binary data files in banary mode.