Guardyoureyes often receives questions regarding the limits of what's permitted in the bedroom. Although there are many levels of holiness that a person should strive for, we live today in a very open world full of big nisyonos. Most Chosson and Kalla teachers do not leave much room for lenience when training young couples. However, being strict in these areas today can sometimes be detrimental to Shalom Bayis and to the spiritual and emotional health of the couple.
Therefore, it is important to state clearly that the bottom-line psak that we have heard in general from most Poskim is that any behavior with your wife that can enhance the intimacy for BOTH OF YOU, bring you closer together and make it an overall more enjoyable experience, is permitted (besides for hotzas zera livatala, which means finishing outside).
However, any behavior or position that one of the partners is not fully comfortable with should definitely be avoided.
A few helpful resources on this topic:
See here from the Shulchan Aruch for the bottom-line Halacha.
Listen to this 10 minute talk by R YY Jacobson on Intimacy.
Rabbi Simcha Feuerman, DHL, LCSW-R, President of Nefesh International, who specializes in Male Sexual Health and Function, recorded a set of shiurim for GuardYourEyes called The Chosson Shmooze You WISH you had but NEVER Got. He talks about the things you really need to know, both about sexual health, relationship health, and what to do when problems and dysfunctions arise. Having worked with couples and individuals for over 25 years, Rabbi Feuerman's insights on these issues are a clear sane voice, with a Torah perspective, in a world of confusion and misinformation. The series is password protected because it deals with intimacy. (Send an email to eyes.guard@gmail.com) for the password if you're married.
See this article called "The Dangers of Misguided Piety" by Rabbi Simcha Feuerman.
See this eBook: עת לפרוש ועת לאהוב by Rabbi Simcha Feuerman.
Download a Kuntris called "Dvar Seser" by a big Tamid Chacham that discusses these inyanim here (I believe in Perek Daled). He brings many solid mekoros for his maskanos.
CAVEAT : All of the above is for normal people who struggle with a normal Yetzer Hara. However for a real addict, Dov (who is clean for over 20 years in SA) says that seeking all sorts of leniencies and enhancements in the bedroom can make a person even sicker and the shalom bayis even worse. Initially it might seem to help, but it can create a monster and become a nightmare. Instead, a real addict has no choice but to learn how to surrender lust and focus more on others, especially his wife. However, this first requires the admission that he (or she) has a real personal problem, rather than just a question about 'sexuality and halocha'. To discuss if you may have an addiction issue or not, you can reach Dov at wequithiding@gmail.com.