Is it permissible for a man to address or write to his ex-wife in a romantic way after marrying another woman? And is it appropriate to keep pictures and cards of his ex-wife in the bedroom with his new wife?

After the iddah (definition) (waiting period) ends, the divorced woman becomes a stranger (ajnabiyyah) to her ex-husband. Therefore, it is not permissible for him to correspond with her, speak to her, be in seclusion with her, or shake hands with her, due to the fitnah (temptation/strife) involved and the violation of Sharia (definition). Likewise, it is not permissible for either of them to keep pictures of the other, because they have become strangers, and looking at them is forbidden, in addition to the problems that keeping pictures can cause in a new marriage. If the divorce was revocable (raj'i), and the couple sees the possibility of establishing the limits of Allah, then it is permissible for him to take her back with a new contract, especially if they have children together. Marrying a second wife is not an impediment to taking back the divorced wife if he is capable of providing for both.