Jmix 1.4 release candidate

Yes, you can use ANY Vaadin component as if you were building a plain Vaadin application. An example for file uploading:

@ViewComponent
private FormLayout form;

@Autowired
private FileStorage fileStorage;

@Subscribe
public void onInit(InitEvent event) {
    MemoryBuffer memoryBuffer = new MemoryBuffer();
    Upload upload = new Upload(memoryBuffer);
    upload.setMaxFiles(1);
    upload.addFinishedListener(event1 -> {
        FileRef fileRef = fileStorage.saveStream(memoryBuffer.getFileName(), memoryBuffer.getInputStream());
        getEditedEntity().setPicture(fileRef);
        updateImage();
    });
    form.add(upload);
}

Will be implemented later.

Use Form Layout