Thanks for the feedback!
And @Symoon, you spotted (
again!) the most important detail of this demo - the used compression, anything else is already seen.
The demo has actually 6 "full-sized" pictures which are compressed with LZ4 and the result sizes are "dramatic"

.
Attached you can find original PNG's converted to RAW's 240x200 (i.e. 8000 bytes), LZ4's are the compressed binaries which were linked into main program. Runtime the images are unpacked directly to HIRES memory.
Although the pictures are not very complex the compression ration is good and the 6502 unpacker is fast!
For who is interested original packer/unpacker sources can be found here:
https://github.com/fadden/fhpack
I've modified them quickly to make them Oric compatible. There is some more work like optimization and clean-up...