Dear Karina,
internally, SPM uses a #scan-by-4 matrix to represent factors and levels. Thus, 4 factors should not be a problem. However, one of them is "reserved" as the "repl" factor and you can only use it if there is a replication factor in the design. In your case fortunately there is one - your "Time" factor. So, if you use the special factor names "subject" and "repl", you have two factors left for "Emotion" and "Face".
I have tried such a model specification on dummy data, see the attached batch. It defines four factors, a sample subject and includes the interaction terms Emotion-vs-Face and the subject constants in the design matrix. First, you should review the error variance settings for each of the four factors. Then you need to specify each subject. The order of images per subject is defined in the "conditions" matrix. Factor levels only need to be specified for the Emotion and Face factors. A duplicate entry of the same factor levels for Emotion and Face is automatically treated as a replication. In the example batch, I have choosen to first specify the scans for replication 1, followed by replication 2. You are free to enter the scans in a different order, you just need to adjust the conditions matrix accordingly.
Hope this helps
Volkmar
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