To add weapons or shields, you'll need the .ITM it corresponds to.
Example:
You Want To Add A Custom Oasis Shield.
1) Create a .dds file that expresses the design you want for the shield.
2) Find a .3dc file that shows the skeleton you want for the shield.
3) If the Item ID for your shield is 39 123, then you'll need to open up the 39.ITM file in your item folder.
4) After that, add the new shield you want in a new row, using the name of your customized .dds file. Use the .3dc file you'd like to go with it, and keep the UNK value at 0.
5) Save it and close it, reopen shstudio, and ensure that the changes match your item.sdata
6) Save and run your item.sql, and restart your server.
7) Enjoy!