Well I thought maybe WAIO or Wood R4 for m3 would work but regardless not really Wood R4 so I failed.
Well according to their website do this but if the loading screen bothers you that much you could switch to alternative firmware where it would be easier.
I have a feeling the loading screen is programmed into a file and cannot be changed easily. Might be a M3 or Dstt clone.
http://www.r4ipocket.com/producte.asp
7.Skin change method
Four files are alternative in the R4iMenu/Skin category: they are TScreen.bmp, BottomInit.bmp, TScreen.bmp and BottomScreen.bmp, which are the operation interface of R4, content in the pictures can be changed at random.
TScreen.bmp -- R4 NDSI Top screen interface after starting the machine
BottomInit.bmp -- R4 NDSI Bottom screen interface after starting the machine
TScreen.bmp -- R4 NDSI Top screen interface for the file category
BottomScreen.bmp -- R4 NDSI Bottom screen interface for the file category
Notice: The above files names can not be changed, picture must be in .bmp format with 8 or 24 digits, picture size must be of 256*192 pixel.
Once your favourite picture is ready, copy the complete category “TF card R4iMenu/ skin” to TF category.
Edit: Well regardless all three of us failed one way or another I hope you figure it out how
It is kind of strange that the R4i SDHC website looks almost the same as the R4i Pocket I guess that could be coincidence.