1. Open UI_DATA_SETUP.ui in Brres viewer and see the file name of English picture with strap that we will replace to Polish.
It's "strapB"
2. Open UI_DATA_SETUP.ui in HexWorkshop (or any hex editor).
3. search text - all instances about "brres" - it's BRRES file header. 11 will be found.
4. find the section between those "brres"-es which has needed file name "strapB" at the end.
5. select and copy (ctrl+C) all data in this section (from "brres" header, including it, up to the next "brres")
It's from 0x00070B94 to 0x00096494.
Create a new file in HexWorkshop and paste (ctrl+V) just copied data into it. Save it "as" at any filename with *.brres extension.
Now you have a brres file with English picture.
6. Download a bunch of tools called "Ctools" - there is a BRRES Editor. Run it.
7. Open your new brres file with English picture in brres editor.
8. Press "import" button (in my version it can be found at the bottom right corner of the window) and select PNG file with your Polish picture.
Now English picture is replaced by Polish. Save file.
File size will be identical to the original strapB.brres file: 150 KB (153 856 bytes).
9. Open it in HexWorkshop (or any Hex editor), select all, ctrl+C.
10. Open UI_DATA_SETUP in hex editor, select all data between 0x00070B94 - 0x00096494 (where you took original picture before).
11. Ctrl+V over old data. It will be replaced.
12. Resave file.
13. Insert your new UI_DATA_SETUP.ui into ISO