Hi all,
i would like to share my solution. After digging deeper into GitHub - merdok/homebridge-webos-tv: Homebridge plugin for LG webOS TVs i found a way to set specific picture mode using pure HA services.
It’s a little bit tricky because it opens allert popup and then after click fires luna action 
This is my script:
living_room_lg_tv_picture_mode:
sequence:
- service: webostv.command
data:
entity_id: media_player.living_room_lg_tv
command: system.notifications/createAlert
payload:
message: >-
{{ picture_mode }}
modal: false
buttons:
- label: "ok"
focus: true
buttonType: "ok"
onClick: "luna://com.webos.settingsservice/setSystemSettings"
params:
category: "picture"
settings:
pictureMode: >-
{{ picture_mode }}
type: "confirm"
isSysReq: true
- delay: 0.6
- service: webostv.button
data:
entity_id: media_player.living_room_lg_tv
button: ENTER
as picture_mode you can pass supported picture mode.
Available picture modes (not all are available on all TVs):
cinema, eco, expert1, expert2, game, normal, photo, sports, technicolor,
vivid, hdrEffect, hdrCinema, hdrCinemaBright, hdrExternal, hdrGame,
hdrStandard, hdrTechnicolor, hdrVivid, dolbyHdrCinema,dolbyHdrCinemaBright,
dolbyHdrDarkAmazon, dolbyHdrGame, dolbyHdrStandard, dolbyHdrVivid, dolbyStandard
You can also play with time of delay.
And also worth to note that this approach can be used to modify other settings eg. energySaving