Cloud computing is nowadays one of the most promising IT technologies, since it provides seemingly unlimited resources on demand at low costs. Hence, different types of applications have been migrated to IaaS environments, e.g. multi-tier (distributed) applications. However, in order to benefit from such characteristics, cloud configurations (i.e. virtual resource configurations) should be designed accordingly to the necessities of the applications. Furthermore, such configurations have to provide the required resources not only at the application deployment-time, but also during the whole application execution time. Hence, adaptive paradigms are required when designing solutions to cloud applications with dynamic resource requirements. Software Product Lines (SPLs) provide great flexibility and a high level of abstraction to describe complete system configurations. Even though SPLs are not commonly used to describe changes after an initial product (configuration) has been created, their inherent characteristics can enable producing the required virtual resource configuration to adapt applications after their initial deployment, i.e., at runtime. In this paper, we present an approach to create and adapt cloud configurations at the IaaS level by using SPLs. We focus on the architectural design of our solution as well as on the possible implementation challenges we could face.