Hi Eugene,
First you could get process picture from repostitoryService.
String imageName = processDefinition.getImageResourceName();
InputStream imageInputStream = repositoryService
.getResourceAsStream(processDefinition.getDeploymentId(),
imageName);
Second you could get activityCoordinates from repositoryService.
ActivityCoordinates ac = repositoryService
.getActivityCoordinates(processDefinitionId, activityName);