Create many files with random content

Since you don't have any other requirements, something like this should work:

#! /bin/bash
for n in {1..1000}; do
    dd if=/dev/urandom of=file$( printf %03d "$n" ).bin bs=1 count=$(( RANDOM + 1024 ))
done

(this needs bash at least for {1..1000}).

A variation with seq, xargs, dd and shuf:

seq -w 1 10 | xargs -n1 -I% sh -c 'dd if=/dev/urandom of=file.% bs=$(shuf -i1-10 -n1) count=1024'

Explanation as requested per comments:

seq -w 1 10 prints a sequence of numbers from 01 to 10

xargs -n1 -I% executes the command sh -c 'dd ... % ...' for each sequence number replacing the % with it

dd if=/dev/urandom of=file.% bs=$(shuf ...) count=1024 creates the files feeded from /dev/urandom with 1024 blocks with a blocksize of

shuf -i1-10 -n1 a random value from 1 to 10

This uses a single pipeline and seems fairly fast, but has the limitation that all of the files are the same size

dd if=/dev/urandom bs=1024 count=10240 | split -a 4 -b 1k - file.

Explanation: Use dd to create 10240*1024 bytes of data; split that into 10240 separate files of 1k each (names will run from 'file.aaaa' through 'file.zzzz')