[Carpetsmoker]

I would do it like this ...

#!/bin/sh

RenameFile()
{
  cd ${1}

  for f in *; do
    nf=$(echo "${f}" | tr ' ' _)

    if [ "${f}" != "${nf}" ]; then
      mv -f "${f}" "${nf}"
    fi

    if [ -d "${nf}" ]; then
      RenameFile "${nf}"
    fi
  done

  cd -
}

find . -name "*.jpg" -or -name Thumbs.db -or -name "*.ini" -delete
find . -type f -exec chmod 644 {} \;
find . -type d -exec chmod 755 {} \;

RenameFile .