Yes, I've used this tool BMRP that Hibernatus links to in his post here:
You can use it for rooms(backgrounds) and objects for export and import. The post states that the tool needs the BM HD PA files for a room background and the files OI OC PA for an object.
My "technique" was:
1) extract all game files in a dumpingtmp folder by running scummrp:
scummrp.exe -ogpd indy3vga . dumpingtmp/
2) find the rooms/objects I wanted to change.
e.g: Extract a room image:
e.g: Extract an object image:
BMRP.EXE -d:dumpingtmp/LF_0079/RO/ -o:0851
3) After editing the extracted BMP image (make sure you kept the pallete intact) you have to repack it back:
e.g for a room image
e.g for an object
BMRP.EXE -c:dumpingtmp/LF_0079/RO/ -o:0851
4) repack the files into the game archived files:
scummrp.exe -igpd indy3vga . dumpingtmp/
5) I think you must reload your translation (if any) after this, because it gets reset by the repacking.
Keep in mind that you should often take backups before you screw something and you are not able to fix it later on or find the cause of an error.
This worked for me flawlessly for the greek translation of the VGA and FMTowns versions of Indy 3 (not EGA though). At least I don't remember any problems, since this was finished a few years ago.