I feel that this radiates energy to the entire arrangement. In such cases you will probably choose to focus on crystals specifically related to these purposes. Green stones are always helpful for healing, and special center pieces might be a statue of Kwan Yin, or a green calcite or aventurine sphere. Frogs and bears, both of which symbolize healing, are appropriate for this kind of altar. For love we generally focus on the pink stones, and if improved communication is part of the state you wish to create you might choose to add aquamarine, chrysocolla, blue lace agate, larimar, turquoise, or amazonite.
Some people like to create angel altars for angelic guidance.
Any symbols of angels work well as centerpieces. Many people like to either vary the elements of their altars or have particular ones related to the seasons. A winter altar might include pine cones, evergreen tree branches, and a focus on clear crystals such as quartz, calcite, danburite, and selenite. Red and green accents often brighten up a winter altar. A spring altar would have a focus on green.