Batch script to rename files in subfolders

Question

I need a script which rename all files in all sub folders of script's root. I did search and found something which works and I can modify (I am a little bit newbie/laic)

@echo off
chcp 65001
setlocal enabledelayedexpansion
set filename=image
set /a x=1
>@rename.txt (
for /r %CD% %%f in (*.jpg) do (
        echo rename "%%f" "!filename!_!x!.jpg"
        rename "%%f" "!filename!_!x!.jpg" 
    set /a x+=1
    )
)
endlocal
pause

But I want this to rename files to random string.

I found a lots of scripts which can generate random strings, but I just can't make them to work inside the FOR brackets.

for now im stuck with

@echo off
chcp 65001
setlocal enabledelayedexpansion
set /a x=%RANDOM%/99
>@rename.txt (
for /r %CD% %%f in (*.jpg) do (
        echo "%%f" renamed to "!x!.jpg"
        rename "%%f" "!x!.jpg"
    set /a x+=%RANDOM%/99
    )
)
endlocal

Which works fine, but has his limitations.

Any help will be appreciated

Answer 1

@echo off
chcp 65001
setlocal enableextensions enabledelayedexpansion
set "alphabet=a b c d f g h i j k l m n p q r s t u v w x y z 0 1 2 3 4 5 6 7 8 9"
    set "size=0"
    for %%a in (%alphabet%) do (
        set "a.!size!=%%a"
        set /a "size+=1"
    )
for /r %CD% %%f in (*.jpg) do (
    set "k="
    for /l %%a in (1 1 64) do (
        set /a "r=!random! %% size"
        for %%b in (!r!) do set "k=!k!!a.%%b!"
    )
    rename "%%f" "!k!.jpg"
   )
endlocal