Wish I had your problem
I customize all of my NUC BIOS with my company logo, use this tool:https://downloadcenter.intel.com/download/22856/Intel-Integrator-Toolkit?product=87570
This will allow you to set the specifications you need in the BIOS, save that BIOS back to a file and then deploy it to your 20 NUCs.
Thank you for contacting the Intel Communities.
The tool provided by cwizardtx would help you to modify the BIOS and its splash screen for sure.
Now, in order to get BIOS modified remotely, it would be required to have an Intel® NUC with the Intel® vPro Technology enabled in it's processor.
The task would be handled by the Intel® Active Management Technology.
Here you can find some information about this technology: Intel® Active Management Technology (Intel® AMT)
The NUCs that are Intel® vPro enabled are: ARK | Compare Intel® Products
-Intel® NUC Kit DC53427HYE
-Intel® NUC Kit NUC5i5MYHE
Additionally, please keep in mind that your server should also be AMT capable to perform this.
If you require any further information or support, do not hesitate to contact us back.