Hi,
There is always a possibility, but as the RUTX theme is absolutely made by us there is a big chance that a lot of elements will not have their placeholders. So if you want to keep the full functionality of our RUTX devices it is better to stick with the default Teltonika theme.
I can suggest that you check the internal folder of the router called "www", there you will find most of the elements used in UI, it will not change the structure, but you can definitely change how your WebUI elements like logo, colors look..
Please note that any changes made to WebUI through www folder will be reset after resetting your device to default settings.
EB.
