Send attached images in teams to another connected user or agent.

Lakshmi_145 -Could you please try the below code for image attachment-
Also refer the sample -Microsoft-Teams-Samples/samples/bot-file-upload/csharp/Bots/TeamsFileUploadBot.cs at main · OfficeDev/Microsoft-Teams-Samples (github.com) 

private async Task ProcessInlineImage(ITurnContext<IMessageActivity> turnContext, CancellationToken cancellationToken)
{
var attachment = turnContext.Activity.Attachments[0];
var client = _clientFactory.CreateClient();

// Get Bot's access token to fetch inline image.
var token = await new MicrosoftAppCredentials(microsoftAppId, microsoftAppPassword).GetTokenAsync();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var responseMessage = await client.GetAsync(attachment.ContentUrl);

// Save the inline image to Files directory.
var filePath = Path.Combine("Files", "ImageFromUser.png");
using (var fileStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None))
{
await responseMessage.Content.CopyToAsync(fileStream);
}

// Create reply with image.
var reply = MessageFactory.Text($"Attachment of {attachment.ContentType} type and size of {responseMessage.Content.Headers.ContentLength} bytes received.");
reply.Attachments = new List<Attachment>() { GetInlineAttachment() };
await turnContext.SendActivityAsync(reply, cancellationToken);
}

private static Attachment GetInlineAttachment()
{
var imagePath = Path.Combine("Files", "ImageFromUser.png");
var imageData = Convert.ToBase64String(File.ReadAllBytes(imagePath));

return new Attachment
{
Name = @"ImageFromUser.png",
ContentType = "image/png",
ContentUrl = $"data&colon;image/png;base64,{imageData}",
};
}