Based on those images, this appears to be a fairly straight-forward run-length encoded 32-bits-per-pixel bitmap format.
The general structure seems to consist of number of records each with a single 'tag' byte followed by a multiple of 4 bytes of RGBA data. These records appear to encapsulate pixel data only, with no dimensions or other metadata.
You cannot prevent patching. There are ways to make reverse engineering harder but the checksum approach is not the best way. There are way more advanced methods, that canmot be compared to a custom made antitampering routine.
Even those advanced methods become eventual studied and cracked.
Either you have to rely on commercial protections (maybe hardeware ...
Here's my go to in Python3: bytes.fromhex('020a0d')
From there you can interpret how you'd like.
Python 3.7.6 (default, Dec 30 2019, 19:38:26)
>>> hex_str = '020a0d'
As an aside, I've found that storing things as ASCII Hex is one of the better RE habits I've gotten into. You can share ...