Reviews fall under fair use for copyright and it is permissible to use artwork from the source material with certain caveats. This should apply to all games you want to review
A good rule of thumb would include things things like:
- Watching the amount of copyrighted material being used. (There is no set figure here but realistically speaking you should be using the minimal amount needed to demonstrate the points of your review).
- Being careful regarding the significance of what you're showing. You don't want to show off the "heart" of the project (which for a romance game is likely to include CGs of pivotal relationship moments or the romantic CGs and ending CGs.) Anything that might affect someone's ability to market their work could conceivably considered the 'heart' of the work even if it amounts to a really small amount of content.
Regarding credit, it's just important to show my studio logo and make note that it is a "Steamberry game."
I don't read blog reviews so this is not something I'll check up on - it's more of an honour system. I trust you won't show off anything that'll make people feel there's no need to play the game. LoL