What is the best incision if I'm prone to keloid scars and interested in getting a breast augmentation? (Photo)

Good morning!I find that the nipple incision heals almost invisibly by 12 weeks postop and has much less likelihood to form a hypertrophic scar when compared to a crease or armpit incision!

For keloid formers, there is not a way to prevent keloids.  In general, the longer the scar or the greater the number of scars, the greater the chance for keloids. 
The only way for sure to avoid keloids is to avoid making an incision. Though the likelihood for developing keloids is low, there is no way to predict their appearance after surgery.
In the broad array of literature as it relates to keloid treatment, there is a global absence of definitive protocols in the management of keloid scars. As an author of "Scars and Scar Revision in Reoperative Plastic and Reconstructive Surgery", I am well versed in the potential treatment options.  One treatment may be helpful for one patient while another treatment may help another patient.
Most fair-skinned patients heal the incisions well, and the scars are barely visible at one year.  However, some patients can develop widened scars, hyperpigmented scars, hypertrophic scars, or keloid scars.  These may require multiple modalities to achieve the best results. 

For a straight forward breast augmentation I would recommend an incision at the inframammary fold (IMF).  I would first recommend having a consultation with a board certified plastic surgeon.  You can discuss your options and preventative treatments postop, such as steroid injections.  In my practice, I recommend that my patients use a silicone based scar cream, such as Biocorneum for the first 6 months to a year.  Best of luck!