Dreaming about your situationship using a toddler's picture as wallpaper on his phone can have several interpretations. Here are a few insights:

1. Symbol of Innocence: The toddler's picture may symbolize innocence and purity. It could reflect your feelings about the relationship, suggesting that there is a desire for a simpler, more innocent connection, or perhaps a longing for a more genuine emotional bond.
2. Desire for Family: If you have thoughts about starting a family or a future with your situationship, the toddler's picture might represent those aspirations. It could indicate a subconscious desire for stability and growth in your relationship.
3. Childlike Qualities: The use of a toddler’s picture could suggest that either you or your situationship is exhibiting childlike behavior. This might relate to playfulness, naivety, or a lack of seriousness in how you are approaching the relationship.
4. Reflecting Your Feelings: The dream might also reflect your feelings about the dynamics of your relationship. If you feel that there is a lack of maturity or commitment, the toddler image could be a metaphor for how you perceive the emotional maturity of the connection.

Consider how you felt in the dream and your current feelings about your situationship. These emotions can provide further clarity on what the dream might mean for you personally.