One way to have the loading screen randomly selected when you start the game would be to load with a batch file like the following.
Note 1: You would need to change your EQ shortcut from pointing to "eqgame.exe patchme" to pointing to your new batchfile.
Note 2: This batch file's coding assumes you have installed your load*.jpg files into a folder called "Loadscreens" inside the "Resources" folder of your EverQuest directory.
File: eqgame.bat
Code:
@Echo Off
Title EverQuest Loader
If Not Exist Resources\Loadscreens\load*.jpg GoTo :NotHere
PushD Resources
If Not Exist loadscreen.jpg.backup If Exist loadscreen.jpg Copy /Y loadscreen.jpg loadscreen.jpg.backup > nul
PushD Loadscreens
Del ..\loadscreen.jpg
:AddLoadscreen
For %%F In (load*.jpg) Do Call :CheckLoadscreen %%F
If Not Exist ..\loadscreen.jpg GoTo :AddLoadscreen
PopD
PopD
Echo Starting EverQuest...
Start /Wait eqgame.exe patchme
PushD Resources
If Exist loadscreen.jpg.backup Copy /Y loadscreen.jpg.backup loadscreen.jpg > nul
PopD
GoTo :EOF
:NotHere
Echo .\Resources\Loadscreens\load*.jpg not found. Make sure you are loading from the EQ directory and have the load screens installed.
GoTo :EOF
:CheckLoadscreen
If /I %Random% LSS 1000 Copy /Y %1 ..\loadscreen.jpg > nul
GoTo :EOF
Tested and working on Windows XP. Should work just as well on Vista.
If you're using Vista, though, make sure you're working in a directory you have Write permissions in, or have the batch file set to Run as Administrator, or it won't be able to copy the files around as it needs to.