To change the titlebox and login buttons go to the folder called " Sprites " then look for your titlebox and login buttons, open them in paint and edit, or whatever els you want.
To add new items you most likely need The Model and the ints, if you aint got the model the items isnt going to look right, if you got the model without the ints you aint geting them item ingame. and you also need to compile. if thats what you are doing
I might be wrong if deltascape client is different then my, if so, sorry.