Brachioplasty can be a challenging surgery when it comes to excising exactly the right amount of skin and tissue. Too much and you can have major complications from trying to close the incisions and too little leads to residual excess skin and fat with a poor shape. I certainly agree with the other comments already posted that it's to soon to properly evaluate the results. If you are not still wrapping your arms or wearing compression sleeves I would consider continuing to do so. If after 6-8 weeks you are still not satisfied with the result I would discuss it with your surgeon. Small revisions are not an uncommon thing and often lead to great results.
Best of luck.
I am sorry to hear about your concerns after arm lifting surgery; although it is still too early to evaluate the outcome of the procedure performed, your concerns seem reasonable, based on the photographs posted. If, in the longer term, you remain concerned, it is likely that your plastic surgeon will be able to improve your outcome with additional skin/tissue removal. Continue to follow up with him/her and communicate questions/concerns directly. Best wishes.
If there's excess skin in the armpit area, be sure to express your concerns to your surgeon and to talk about possible corrective options. You may have to wait at least 3 months before a revision though but this depends on your surgeon's recommendation. Typically in an arm lift, the excision extends from near the elbow area to the armpit area and includes removing excess skin from the armpit area as well. Good luck.
Based on your pictures, it appears the there is still lax skin in the upper arm, near the armpit. I would ask your surgeon what he/she feels about your results, and what to expect - and you would not be wrong to ask the area to be corrected.