Did you get an error message?
there should be no limit in the picture number other than record count in the databse .... i have more than 30.000 pic in coppermine and have no problems adding even more (thousands more btw ... ) ....
edit: just read agin an saw your note "they just dont show" ..... try to rename the pics. Coppermine doesnt like pics with the same name, even if they are to be added to different albums ....