Is there a limited number of features for QSVM in Qiskit-Aqua?

Here is a tutorial that uses three classes! If you want to use more than two classes, you need a multiclass_extension which is provided as a parameter to the QSVM

svm = QSVM(feature_map, training_input, test_input, total_array,
          multiclass_extension=AllPairs(_QSVM_Estimator, [feature_map]))

As shown in the tutorial. There are a few multiclass extensions to choose from, which are all here.