As people finish running through the retail levels, they might want to play some of the user made levels that are around.
I know of a few sites that host Blood maps and mods. A few good ones to start off with, I'm sure the crowd knows of more.
Blood map collections:
http://www.blood.freeminded.de/, I would highly recommend "Gods, the Epic Trilogy"
Blood mods:
RATM - http://www.moddb.com/mods/ratm
Bloody Pulp Fiction - http://www.moddb.com/mods/bloody-pulp-fiction

I actually made a new single player/coop/deathmatch map like two months ago.
I also have several unreleased maps.
You can find some here: http://itburn.tripod.com/archblood.htm
I also recommend Gods, it's completely insane.
Also try the "lost evil" map if you can find it.
I'll upload some maps to your site!

Good to see you here and spreading the great user made maps, Dusty. I bought Blood from this site recently so I could finally actually own the game without going through other means to get it. ;)

I have not uploaded it to any Blood sites yet, but this is a conversion of a popular fast paced Doom 2 deathmatch map (Dwango5 map01) that I converted to Blood recently.
http://www.mediafire.com/?nyzcd2tz1ty

Not to sound like a total fool but how do you load these maps with the GoG version of the game?

That depends on the collection. If it's just a map you can add the -map [map_name].map to the execution line within your dosboxBlood.conf file.
All the way at the bottom you will see some entries:
cls
blood
exit
just make the blood line read:
blood -map [map_name].map
if it is an entire chapter, you will need to reference the ini file.
blood -ini [ini_name].ini
Some of the others have their own launchers which can be confusing, but that's the short of it.

Thanks! I'll give it a whirl and see if my brain can make it work.

Thanks for the recommendations guys! I'm one of the brothers who made the God's maps. Nice to know they're still enjoyable :)
I'm looking at uploading them (and the largest Blood map ever made, which I'm pretty sure was never officially released) to a bit more of a permanent home soon.

Good to hear! It's a shame to think of how many good user made maps have been lost to the internet. Gods has always been one of my favorites.

Sorry to be an idiot and ask again, but how do you play mod levels on the GOG version of this game? I have a heap of self made levels languishing on floppy discs that I would love to re-play. Any help would be greatly appreciated.

Sorry if I was a little vague earlier. What do you need help with, locating your conf file?

@DustyStyx
Thank you very much for your prompt reply. I was really struggling with the whole thing! I used to type the level names in with DOS back in the day and now wasn't sure how to go about doing it as the game now launches immediately without giving you the opportunity to type anything before hand.

Subsequently, I have been directed to some links for a launcher that should hopefully rectify the problem. Should I be unable to make that work though, I hope you won't mind me bothering you again!

But where is the dosboxBlood.conf file ?
And where do I put the user-maps files ?

thanks for who reply

Well, it could be any number of places, but if you are using the default DOSBox build that GoG shipped out, it should be in either "%programFiles%\GoG.com\One Unit Whole Blood" or "%programFiles(x86)%\GoG.com\One Unit Whole Blood" if you are running 64bit.

You should put the user made maps in the same directory as Blood.exe