PDF file creator

You can create a bunch of random letters as PDF files.

Distort PDF files

You can imitate a PDF from scan or fax with ImageMagick's convert:

convert -density 150 letter.pdf -colorspace gray -linear-stretch 3.5%x10% -blur 0x1 -attenuate 0.25 +noise Gaussian -rotate 0.75 as-scanned.pdf

see ImageMagick security policy

Keyword driven image fetcher

You can fetch scaled down images for keywords from Pixabay.

Create large images with ImageMagick

JPG images with large file sizes

180 MB -> convert -size 8000x8000 xc: +noise Random -quality 100% random.jpg
55 MB -> convert -size 4000x5000 xc: +noise Random -quality 100% random.jpg
25 MB -> convert -size 3000x3000 xc: +noise Random -quality 100% random.jpg

Just use other file suffixes to use different image encodings

convert -size 8000x8000 xc: +noise Random -quality 100% random.png