This is dependent on the 'urf' (custom) of where you reside. Generally not posting pictures is better however if the hijab is not practiced and the limits of jurisprudence are not abided by, then it becomes haram. If the limits of religion are observed, one should note that such an action may result in other problems or sins for example can cause another to get attracted etc.
In general, if one knows that an act would lead to another act which is haram or may cause problems to arise, then carrying out the said act is problematic however if no problem would arise then as per religious law, there is no problem even though it may not be recommended (to do the particular act)