A site about Talend
If your designing you're own component, then you'll need an image file that will represent your component in the Component Palette and in your Job designs. You will not be able to publish your components without this file.
Talend does provide a default image file however, there is little value in using this as all of your component would look the same.
Often, your components will be for interfacing with another vendor's software, so using an image of their logo may be useful and, if you have multiple components to support a single vendor, you can use variations of these, for example, adding arrows that indicate if the component either starts or end data flow. You can see many examples of this, such as the Salesforce components that use variations of one of their logos. Alternatively, you may create your own or look for one of the many free images that are available online.
Whatever you do. try to make your image as meaningful as possible, within the size constraint available.
The specification of your image file is fairly straightforward. It must be Portable Network Graphics (PNG) format and be 32 pixels by 32 pixels.
The naming convention for the image file is
tMyComponent is the name of your component.
Some of the other standard Talend components have other image files. Some of these are of different sizes, for example,
tUniqRow_icon16.png and a large number of the components have a white image, for example,
tAccessInput_icon32_white.png. I do not know why this is, so I have discounted these.